Human Health and Ecological Risk Assessment

for the Use of Wildlife Damage Management Methods

by APHIS Wildlife Services

Chapter XXIV

USE OF REGISTERED CHEMICAL 

REPELLENTS IN WILDLIFE DAMAGE 

MANAGEMENT

May 2023
i

EXECUTIVE SUMMARY

Chemical repellents are a tool used to alter animal behavior under various agricultural and 

nonagricultural uses. The United States Department of Agriculture (USDA), Animal and Plant 

Health Inspection Service (APHIS), Wildlife Services (WS) Program uses chemical repellents to 

reduce bird conflicts at airports, reduce bird damage to crops and property, and reduce mammal 

damage to gardens, crops, and property. The primary target bird species WS repels include 

flocking passerine bird species, for example, European starlings and blackbirds, waterfowl, and 

gulls. The primary target mammal species include white-tailed deer and rabbits.

Chemical substances that are marketed or distributed for use as repellents (hereafter called 

chemical repellents) are divided into those that require federal registration under the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) and those classified as minimum risk 

pesticides (MRPs) under FIFRA Section 25(b). This risk assessment will cover registered 

repellents. MRPs are covered in another Risk Assessment.

APHIS evaluated the potential human health and ecological risks from the proposed WS use of

the registered active ingredients ammonium soaps of fatty acids, anthraquinone, capsaicin, egg 

solids, garlic oil, methyl anthranilate, naphthalene, oil of black pepper, piperine, polybutene, sulfur,

thiram, and coyote and fox urines as registered active ingredients in chemical repellents used or 

potentially used in its animal damage management program. WS does not anticipate adverse 

human health effects from their use of chemical repellents based on the label requirements, WS 

use pattern, and environmental fate of the repellents. Adherence to the labels’ personal protective 

equipment requirements minimizes potential exposure to workers. Similarly, WS does not expect 

its use of chemical repellents to impact non-target aquatic and terrestrial species based on the 

repellents’ toxicity profiles, label requirements, and WS use patterns. 
ii

Table of Contents

GLOSSARY OF TERMS AND ABBREVIATIONS...................................................................... 1

1 INTRODUCTION .................................................................................................................... 3

1.1 WS Use Pattern ........................................................................................................... 5

1.2 Individual Chemical Risk Assessment Organization..................................................... 8

2 AMMONIUM SOAPS OF FATTY ACIDS................................................................................. 9

2.1 Problem Formulation ........................................................................................................ 9

2.2 Dose-Response Assessment...........................................................................................11

2.3 Exposure Assessment and Risk Characterization............................................................14

3 ANTHRAQUINONE................................................................................................................15

3.1 Problem Formulation .......................................................................................................15

3.2 Dose-Response Assessment...........................................................................................17

3.3 Exposure Assessment and Risk Characterization............................................................21

4 CAPSAICIN ...........................................................................................................................23

4.1 Problem Formulation .......................................................................................................23

4.2 Dose-Response Assessment...........................................................................................24

4.3 Exposure Assessment and Risk Characterization............................................................25

5 EGG SOLIDS.........................................................................................................................26

5.1 Problem Formulation .......................................................................................................26

5.2 Dose-Response Assessment...........................................................................................27

5.3 Exposure Assessment and Risk Characterization............................................................28

6 GARLIC OIL...........................................................................................................................28

6.1 Problem Formulation .......................................................................................................28

6.2 Dose-Response Assessment...........................................................................................29

6.3 Exposure Assessment and Risk Characterization............................................................30

7 METHYL ANTHRANILATE ....................................................................................................30

7.1 Problem Formulation .......................................................................................................30

7.2 Dose-Response Assessment...........................................................................................32

7.3 Exposure Assessment and Risk Characterization............................................................34

8 NAPHTHALENE ....................................................................................................................35

8.1 Problem Formulation .......................................................................................................35

8.2 Dose-Response Assessment...........................................................................................37

8.3 Exposure Assessment and Risk Characterization............................................................40
iii

9 OIL OF BLACK PEPPER/PIPERINE......................................................................................42

9.1 Problem Formulation .......................................................................................................42

9.2 Dose-Response Assessment...........................................................................................43

9.3 Exposure Assessment and Risk Characterization............................................................44

10 POLYBUTENE.....................................................................................................................44

10.1 Problem Formulation .....................................................................................................44

10.2 Dose-Response Assessment.........................................................................................45

10.3 Exposure Assessment and Risk Characterization..........................................................47

11 SULFUR ..............................................................................................................................49

11.1 Problem Formulation .....................................................................................................49

11.2 Dose-Response Assessment.........................................................................................50

11.3 Exposure Assessment and Risk Characterization..........................................................51

12 THIRAM...............................................................................................................................52

12.1 Problem Formulation .....................................................................................................52

12.2 Dose-Response Assessment.........................................................................................54

12.3 Exposure Assessment and Risk Characterization..........................................................59

13 URINES, COYOTE, AND FOX.............................................................................................61

13.1 Problem Formulation .....................................................................................................61

13.2 Dose-Response Assessment.........................................................................................62

13.3 Exposure Assessment and Risk Characterization..........................................................63

14 UNCERTAINTIES AND CUMULATIVE IMPACTS ...............................................................64

15 SUMMARY...........................................................................................................................68

16 LITERATURE CITED...........................................................................................................69

17 PREPARERS: WRITERS, EDITORS, AND REVIEWERS ...................................................76

List of Tables

Table 1 The annual average number of animals dispersed with chemical repellents and states 

where applied by WS in WDM during FY11–FY15 and FY16–FY20. ......................................... 6

Table 2. The annual average number of gallons of chemical repellents applied by WS in WDM 

during FY11–FY15 and FY16–FY20 for all products with the number of work tasks associated 

with the applications................................................................................................................... 6

Table 3. The annual average number of pounds/gallons of chemical repellents distributed by WS 

in WDM for FY11–FY15 and FY16–FY20 under all product labels............................................. 8
iv

Table 4 The chemical name and CAS number for the individual C8- to C18-saturated and C18-

unsaturated fatty acids ammonium salts within the pesticide active ingredient ammonium soaps 

of fatty acids (CAS Number 84776-33-0).................................................................................... 9

Table 5 Acute and chronic toxicity to aquatic vertebrates and invertebrates for ammonium soaps 

of fatty acids..............................................................................................................................12

Table 6. Acute oral median lethality and subacute dietary toxicity studies for mammals and birds

for ammonium soaps of fatty acids............................................................................................13

Table 7 Acute oral median lethality studies for mammals for technical anthraquinone and an enduse product...............................................................................................................................17

Table 8. Acute and chronic toxicity to aquatic vertebrates and invertebrates for anthraquinone.

.................................................................................................................................................20

Table 9. Acute oral median lethality and subacute dietary toxicity studies for mammals and birds

for anthraquinone......................................................................................................................21

Table 10 Acute oral median lethality studies for mammals for Methyl anthranilate. ...................32

Table 11 Acute and chronic toxicity to aquatic vertebrates and invertebrates for methyl 

anthranilate...............................................................................................................................33

Table 12 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds 

for methyl anthranilate...............................................................................................................34

Table 13 Acute and chronic toxicity to aquatic vertebrates and invertebrates for naphthalene. .40

Table 14 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds 

for naphthalene.........................................................................................................................40

Table 15 Acute oral median lethality studies for mammals for Polybutene ................................46

Table 16 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds 

for polybutene. ..........................................................................................................................47

Table 17 Acute and chronic toxicity to aquatic vertebrates and invertebrates for sulfur.............51

Table 18 Acute and chronic toxicity to aquatic vertebrates and invertebrates for thiram............58

Table 19 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds 

for thiram...................................................................................................................................59

Table 20 Acute and chronic toxicity to aquatic vertebrates and invertebrates for urea...............63

Table 21 Toxicity studies for mammals, birds, and terrestrial invertebrates for urea..................63

Table 22. Summary of chemical repellent toxicity to humans. ...................................................65

Table 23. Summary of chemical repellent acute toxicity to aquatic and terrestrial species. .......67
1

GLOSSARY OF TERMS AND ABBREVIATIONS

μg Microgram

a.i. Active ingredient

bw Body weight

CAS Chemical Abstract Service

CDC Center for Disease Control and Prevention

EC50 Median effect concentration. A statistically derived concentration of a substance 

that can be expected to cause an effect in 50% of test organisms. It is usually 

expressed as a weight of a substance per weight or volume of water or air, e.g., 

mg/L.

FDA Food and Drug Administration

FY The federal Fiscal Year, which is October 1–September 30.

g Gram

GRAS Generally Recognized as Safe

IC50 Median inhibitory concentration. A statistically derived concentration of a 

substance that can be expected to inhibit a biological process or response by 50%

in an enzyme, cell, or microorganism. It is usually expressed as a weight of a 

substance per weight or volume of water or air, e.g., mg/L.

IDS Incident Data System

kg Kilogram

kg-bw Kilogram of body weight

kg-diet Kilogram of diet

lb Pound

L Liter

LC50 Median lethal concentration. A statistically derived concentration of a substance 

that can be expected to cause death in 50% of test animals. It is usually expressed 

as a weight of a substance per weight or volume of water, air or feed, e.g., mg/L, 

mg/kg-bw.

LD50 Median lethal dose. A statistically derived single dose that can be expected to 

cause death in 50% of the test animals when administered by the route indicated 
2

(oral, dermal, inhalation). It is expressed as a weight of substance per unit weight 

of animal, e.g., mg/kg.

LOAEC Lowest observed adverse effect concentration. The lowest dose concentration of 

a substance that under defined conditions of exposure causes an 

observable/detectable adverse effect.

mg Milligram

mm Hg Millimeter of mercury

NIOSH National Institute for Occupational Safety and Health

NOAEC No observed adverse effect concentration. The highest dose concentration of a 

substance that under defined conditions of exposure causes no 

observable/detectable adverse effect.

NOAEL No observed adverse effect level. The highest dose level of a substance that under 

defined conditions of exposure causes no observable/detectable adverse effect.

OPP Office of Pesticide Programs, USEPA

PPE Personal protective equipment

RfD Reference dose. An estimate, with uncertainty spanning perhaps an order of 

magnitude, of a daily oral exposure to the human population (including sensitive 

subgroups) that is likely to be without an appreciable risk of deleterious effects 

during a lifetime.

SENSOR Sentinel Event Notification System for Occupational Risk-Pesticides

Tolerance Maximum amount of pesticide residues allowed on or in food or feed.

USEPA U.S. Environmental Protection Agency

WDM Wildlife damage management

WT Work tasks

w/w Weight by weight
3

1 INTRODUCTION

The U.S. Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS), 

Wildlife Services (WS) employees conduct wildlife damage management (WDM) activities, which 

include the use of chemical repellents as a WDM tool. WS uses chemical repellents to reduce 

bird conflicts at airports, reduce bird damage to crops and property, and reduce mammal damage 

to gardens, crops, and property. The primary target bird species WS repels include flocking 

passerine bird species (e.g., European starlings1 and blackbirds2), waterfowl, and gulls. The 

primary target mammal species include white-tailed deer and rabbits. Successful application of 

repellents to target specific animals requires 1) knowledge of the animal’s learning and sensory 

abilities; 2) an understanding that repellents are regulated as pesticides; 3) are used to deter 

animal activity while not causing permanent harm or injury and may require continual training with 

populations that turn over frequently; and 4) understanding that repellents work best when the 

animal can find alternative resources (e.g., food, shelter), otherwise the animal may undergo

survival hardship (Clark and Avery 2013).

This human health and ecological risk assessment provides a qualitative evaluation of risks and 

hazards to human health and the environment, including non-target fish and wildlife, because of

exposure to chemical repellents from proposed WS uses, which are limited and targeted in scope 

to repelling wildlife from damage situations. The methods used to assess potential human health 

effects follow standard regulatory guidance and methodologies (National Research Council 1983) 

and generally conform to other Federal agencies such as the U.S. Environmental Protection 

Agency (USEPA 2022f). The methods used to assess potential ecological risk to non-target fish 

and wildlife generally follow USEPA (2022f) methodologies.

This risk assessment is divided into four sections: problem formulation (identifying hazard), 

toxicity assessment (dose-response assessment), and exposure assessment (identifying 

potentially exposed populations and determining potential exposure pathways for these 

populations). Lastly, the toxicity and exposure assessment information is combined to 

characterize risk (determining whether there is adverse human health or ecological risk). This risk 

assessment also includes a discussion of the uncertainties associated with the risk assessment 

and cumulative effects.

Registered Repellent Products

Repellents are a favored method in WDM because they are a nonlethal way to reduce damage

from mammals, birds, and reptiles (Fagerstone 2002). Published investigations regarding the 

research and development of chemical substances as repellents date back to the 1830s. 

Identification of the mode of action (e.g., olfactory, taste, pain, conditioned avoidance, or fear), 

the target species or groups (e.g., blackbirds, waterfowl, or deer), efficacy, cost per area, 

1 Scientific names are given in the Risk Assessment Introduction Chapter I, unless first time used.

2 Generic use of blackbirds for this risk assessment includes specific species of blackbirds, cowbirds, and grackles as found on product

labels.
4

availability, and potential hazards are considerations in these studies mirroring the public 

concerns. 

Chemical repellents can be grouped by mode of action: chemicals that animals reflexively avoid

because they irritate the peripheral chemical senses (e.g., taste or smell) and chemicals that 

cause gastrointestinal illness and learned avoidance (Sayre and Clark 2001). Many repellents are 

naturally occurring substances and work by emitting an odor that evokes fear or an undesired 

taste. Repellents are often sprinkled on or hung within the area to be protected or sprayed on 

plants or other surfaces to prevent damage or loss. Liquid products can also be soaked into ropes 

or rags and hung up or dispersed around the area to be protected. Some products cannot be 

applied to growing or edible portions of agricultural crops because the product may damage the 

crop, make the plant unpalatable for human consumption, or the product is not approved for food 

or feed uses. Many factors can affect repellent efficacy. These factors can include the availability 

of alternative foods, the palatability of treated plants, and the number and density of animals 

inflicting problems (Nolte et al. 1994, Trent et al. 2001).

Chemical substances that are marketed or distributed for use as repellents (hereafter called 

chemical repellents) are divided into those that require federal registration under the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) and those classified as minimum risk 

pesticides (MRPs) under FIFRA Section 25(b). This risk assessment will cover registered 

repellents. MRPs are covered in another Risk Assessment.

Of the repellent products that require federal registration, WS has used products containing the 

registered active ingredients ammonium soaps of fatty acids, anthraquinone, egg solids, 

capsaicin, garlic oil, methyl anthranilate, naphthalene, oil of black pepper, and piperidine, 1-

[(2E,4E)-5-(1,3-benzodioxol-5-yl)-1-oxo-2,4-pentadienyl]- (hereafter, called piperine), and sulfur. 

WS has distributed registered repellent products containing additional repellent active ingredients, 

and those are briefly summarized. WS may potentially use registered repellent products 

containing thiram, polybutene, or coyote and/or fox urines in the future, which are also included 

in this risk assessment.

Chemical repellents come in various commercial “ready-to-use” and concentrate products. 

Registered products must have USEPA-approved labels and instructions to guide their 

applications. USEPA classifies most vertebrate repellents as general-use or unclassified 

pesticides rather than restricted use pesticides (RUPs). General-use pesticides can be applied 

without a certified applicator license in most states and U.S. territories. However, some states 

and territories require that commercial and public pesticide applicators are also licensed by the 

state before applying general-use products. None of the registered active ingredients discussed 

in this risk assessment are restricted use pesticides.

Chemical repellents can be used for a wide variety of target pest animals. Repellents can be used 

in various sites, including agricultural fields and gardens, residences and other structures, and 

airports. Many repellents can also be applied at food use sites (e.g., agricultural crops grown for 
5

consumption by an organism) when USEPA has approved pesticide tolerances3 or tolerance 

exemptions for those food uses for all active and inert ingredient(s) contained in the products.

Most registered vertebrate repellents target mammalian herbivores (e.g., deer, rabbits) and avian 

herbivores (e.g., Canada geese and other waterfowl), and omnivores (e.g., flocking birds such 

as gulls, European starlings, and blackbirds). Section 2(ee) of FIFRA is a provision that presents 

special circumstances where it is permissible to use a pesticide in a manner for which it is not 

specifically labeled (e.g., use on an alternative target pest species when the label does not prohibit 

use on target species not listed on the label). A few repellents are used annually to protect human 

health and safety.

1.1 WS Use Pattern

The registered chemical repellents WS has used, sold, or distributed are given in Tables 1, 2, and 

3. Table 1 provides the estimated animals repelled and states where WS used the products. It 

should be noted that it is not always possible to estimate the number of birds dispersed for all 

uses of these products by WS personnel in the MIS4

. It can be challenging to assess the number 

of birds repelled, especially when used in areas where historic damage has occurred (e.g., a 

runoff pond near a runway where migratory waterfowl may land), but wildlife is not currently 

present. WS personnel do not have to enter the number of animals repelled in the MIS for applied 

repellents. If the numbers of animals repelled were not entered in MIS, they were estimated as 

follows, 1,000 for small flocking birds, 100 for large flocking birds, and 10 for mammals, large nonflocking birds and reptiles for every one gallon or 3 pounds of product used. Table 2 provides the 

quantity of each repellent applied and the associated work tasks. Table 3 provides the quantity of 

each product distributed to producers or homeowners to resolve the problems.

WS repelled an annual average of 49,112 target species with chemical repellents between FY115

and FY15 from areas where they were causing damage in 12 states. Between FY16 and FY20, 

WS repelled an annual average of 5,140 animals in 9 states. The use of methyl anthranilate and 

anthraquinone dropped off between the two periods. Blackbirds (77%) and Canada geese (20%) 

were the primary targeted species from FY11 to FY15, while Canada geese (95%) were the 

primary targeted species from FY16 to FY20. Overall, 16 and 10 known species were repelled 

during each time frame, respectively. WS had minor uses of naphthalene and sulfur to repel 

snakes, ammonium soaps of fatty acids to repel deer, and capsaicin, oil of black pepper, and 

piperine to repel feral house cats and black bears (Table 1).

WS used an annual average of 99 gallons of anthraquinone products in 45 work tasks and 8.2

gallons of methyl anthranilate products in 13 work tasks, and 0.2 gallons of capsaicin and oil of 

black pepper product in 0.2 work tasks to resolve problems at airports, orchards, parks, and turf 

from FY11 to FY15 (Table 2). This work involved 6 different products for repelling animals. From 

3Maximum amount of pesticide residues allowed on or in food or feed.

4MIS - Computer-based Management Information System used for tracking APHIS-WS-WDM activities nationwide. Throughout the 

text, data for a year (i.e. FY11 (next footnote)) will be given and is from the MIS. MIS reports will not be referenced in the text or 

Literature Cited Section because MIS reports are not kept on file. A database is kept that allows queries to be made to retrieve the 

information needed.

5FY11 equals the federal Fiscal Year 2011, which is October 1 2010–September 30 2011 (the year is denoted by FY12, FY13, ...).
6

FY16 to FY20, WS personnel annually averaged the application of 48.3 gallons of anthraquinone

products in 21 work tasks, 17.1 gallons of methyl anthranilate products in 7.4 work tasks, 2 gallons 

of products containing ammonium soaps of fatty acids in 1 work task, 0.3 gallons of a product

containing capsaicin and oil of black pepper in 0.6 work tasks, 0.01 gallons of products containing 

capsaicin, oil of black pepper, and piperine compound in 0.2 work tasks, and 0.2 pounds of 

naphthalene and sulfur products in 0.2 work tasks to protect airports, gardens, and property (e.g., 

parks and grass on private land).

Table 1 The annual average number of animals dispersed with chemical repellents and states where 

applied by WS in WDM during FY11–FY15 and FY16–FY20.

ANNUAL AVERAGE CHEMICAL REPELLENTS USED, SPECIES, AND NUMBER REPELLED

Species FY11–FY15 FY16–FY20

Repelled States Used Repelled States Used

Anthraquinone

Canada Goose 9,898 IL PA 4,830 IL WI

Total (1 spp.) 9,898 2 States 4,830 2 States

Methyl Anthranilate

European Starling* 13,183 NC OR PA VA 61 NC VA

Red-winged Blackbird 220 NH 2 VA

Common Grackle 1,435 NH PA - -

Boat-tailed Grackle 600 FL - -

Brown-headed Cowbird 220 NH - -

Mixed Blackbird spp.** 22,240 FL NH PA 15 VA

Mourning Dove 340 AL - -

Purple Martin 1 VA - -

Barn Swallow 30 WV - -

House Sparrow* 101 NC NH - -

Canada Goose 600 NE 128 MO OR VA WI

Laughing Gull 100 VA 64 VA

Ring-billed Gull 66 WI 5 VA

Herring Gull 66 WI 24 VA

Black-crowned Night-Heron 10 PA - -

Northern Flicker 2 OR - -

Total (15 spp.) 39,214 10 States 299 5 States

Naphthalene/Sulfur

Western Diamondback Rattlesnake - - 0.2 TX

Total (1 sp.) - - 0.2 1 State

Ammonium Soaps of Fatty Acids

Mule Deer - - 8 CA

Total (1 sp.) - - 8 1 State

Capsaicin/Oil of Black Pepper/Piperine

Feral House Cat* - - 3 PA

Louisiana Black Bear 0.2 LA - -

Total (2 spp.) 0.2 1 State 3 1 State

GRAND TOTAL (19 spp.) 49,112 12 States 5,140 9 States

* Introduced species

** All species were already counted in the total species

WS State Offices and personnel also provide the public with some chemical repellent products, 

mainly in cooperation with state agencies that manage game animals such as white-tailed deer 

to lessen problems for farmers and property owners from their damage. From FY11 to FY20, 

WS distributed an annual average of 0.6 pounds of products containing egg solids; 4.1 gallons 
7 

of products containing egg solids, capsaicin, and garlic oil; 8 gallons of products containing 

denatonium saccharide (which is no longer a registered active ingredient in any product) and 

Table 2. The annual average number of gallons of chemical repellents applied by WS in WDM during 

FY11–FY15 and FY16–FY20 for all products with the number of work tasks associated with the

applications.

a This product and all other registered 50% w/w anthraquinone products were canceled as of September 2021. The 

remaining anthraquinone products are 18.6% w/w anthraquinone or lower.

b This registration was transferred to Avian Enterprises, LLC in March 2012. c This registration was transferred to Avian Enterprises Limited, LLC, in December 2015.

thymol; 3.6 gallons of products containing ammonium soaps of fatty acids; 2.6 gallons of 

anthraquinone products, and 0.9 gallons of methyl anthranilate products (Table 3). Of the 21 

average annual work tasks associated with distributing repellents from FY11 to FY20, WS 

responded to public requests involving white-tailed deer (94% of requests), Canada geese (3%), 

eastern cottontail rabbits (1%), house sparrows (1%), woodchucks (0.5%), and wild turkeys 

(0.5%). 

ANNUAL AVERAGE CHEMICAL REPELLENTS USED BY WS DURING FY11–FY15 AND FY16–FY20 

Active Ingredient(s) 

(% w/w, CAS Number) Product Name

USEPA 

Registration

Number

FY11–FY15 FY16–FY20 

Applied 

(gal or lb) WTs Applied (gal or lb) WTs

Anthraquinone (50%, 84-65-1) Flight Control®

Plus 69969-1a 99 gal 45 48.3 gal 21

Methyl Anthranilate

(20%, 134-20-3) 

Avian Control® 33162-1, then 

88889-1b 2.8 gal 6 0.03 gal 0.2

Avian Fog Force®

TR 91897-4 0.1 gal 1 - - 

Methyl Anthranilate

(14.5%, 134-20-3)

RejeX-it

® AG 39

or Avian Migrate®

58035-9, then 

91897-3c 1.3 gal 1 0.03 gal 0.2

Methyl Anthranilate

(40%, 134-20-3) 

RejeX-it

® TP-40 or 

RejeX-it Fog 

Force®

58035-7, then 

91897-1c 4.0 gal 5 1.6 gal 7 

Ammonium Soaps of Fatty 

Acids (13.8%, 84776-33-0) Hinder® 5481-508 - - 2 gal 1 

Capsaicin (0.032%, 404-86-4)

Oil of Black Pepper (0.48%, 

8006-82-4) 

Piperine(0.185%)

Havahart® Critter 

Ridder® 50932-10 - - 0.01 gal 0.2

Capsaicin (unknown % w/w, 

404-86-4) 

Oil of Black Pepper (unknown 

% w/w, 8006-82-4) 

Possibly other active 

ingredients

Not recorded Not recorded 0.2 gal 0.2 0.3 gal 0.6

Naphthalene (7%, 91-20-3) 

Sulfur (28%, 7704-34-9) 

Snake-A-Way®

Snake Repelling 

Granules

58630-1 - - 0.2 lb 0.2

TOTAL 9 Products - 107.4 gal 58.2 52.27 gal

0.2 lb 30.4
8 

Table 3. The annual average number of pounds/gallons of chemical repellents distributed by WS in WDM 

for FY11–FY15 and FY16–FY20 under all product labels.

a Denatonium saccharide is no longer registered for use in any pesticide products. This product and all remaining products 

containing denatonium saccharide were canceled in 2015. b This registration was transferred to Avian Enterprises, LLC in March 2012.

c This product and all other registered 50% w/w anthraquinone products were canceled as of September 2021. The remaining 

anthraquinone products are 18.6% w/w anthraquinone or lower. 

1.2 Individual Chemical Risk Assessment Organization

WS uses the following registered chemical active ingredients covered in this risk assessment: 

ammonium soaps of fatty acids, anthraquinone, capsaicin, egg solids, garlic oil, methyl 

anthranilate, naphthalene, oil of black pepper, piperine, and sulfur. WS may also use thiram, 

polybutene, and coyote and/or fox urines in the future. A problem formulation, dose-response 

assessment, exposure assessment, and risk characterization are provided below for each 

registered active ingredient used or potentially used by WS in the future. The problem formulation 

section covers each registered active ingredient’s chemical description, product use, physical and 

chemical properties, environmental fate, and hazard identification. Environmental fate describes 

how chemicals move and degrade in the environment. The environmental fate processes include 

1) persistence, degradation, and mobility in soil; 2) movement to air; 3) migration potential to 

groundwater and surface water; 4) degradation in water; and 5) plant uptake.

The dose-response assessment section discusses the dose levels (toxicity criteria) for potential 

human health effects, including acute and chronic toxicity. It also discusses available ecological 

effects data for terrestrial and aquatic species. Available acute and chronic toxicity data are 

summarized for all major taxa. They will be integrated with the exposure analysis section to 

characterize the risk of chemical repellents to non-target species. Information in this section was 

ANNUAL AVERAGE CHEMICAL REPELLENTS DISTRIBUTED BY WS DURING FY11–FY15 AND FY16–FY20

Active Ingredient(s)

(% w/w, CAS Number) Product Name USEPA Reg. No.

FY11–FY15 

Distributed

FY16–FY20 

Distributed

Eggs Solids (4.63%, 51609-52-

0)

Deer Away® Deer and Rabbit 

Repellent Ready-to-Use 50932-8 0.6 lb - 

Eggs Solids (6.25%, 51609-52-

0) 

Capsaicin (0.0045%, 404-86-4) 

Garlic Oil (0.005%, 8000-78-0)

Deer-Off® Deer, Rabbit, and 

Squirrel Repellent 67356-1 3.7 gal 0.4 gal

Denatonium Saccharidea

(0.65%, 90823-38-4) 

Thymol (0.35%, 89-83-8)

Ro-pel® Tree Squirrel, Vole, 

Dog, and Cat Repellent 81117-1a 8.0 gal - 

Ammonium Soaps of Fatty 

Acids (13.8%, 84776-33-0)

Hinder®-H Deer & Rabbit

Repellent 8119-7 0.8 gal 0.4 gal

Ammonium Soaps of Fatty 

Acids (0.66%, 84776-33-0)

Hinder® Deer & Rabbit

Repellent 8119-8 2.2 gal 0.2 gal

Methyl Anthranilate (20%, 134-

20-3) Avian Control®

33162-1, 

then 

88889-1b

0.6 gal - 

Methyl Anthranilate (20.72%, 

134-20-3)

Liquid Fence® Goose

Repellent 72041-2 0.2 gal 0.1 gal

Anthraquinone (50%, 84-65-1) Flight Control® Plus 69969-1c 2.4 gal 0.2 gal

TOTAL 8 Products 17.9 gal. 0.6 lb 1.3 gal
9 

gathered from online databases and searches for relevant peer-reviewed and other published 

literature.

Unless otherwise specified, the toxicity of the technical a.i. for non-target mammals and birds was

assumed to be similar to the toxicity of the end-use formulations, which is a conservative 

approach. The toxicity of degradants and metabolites of the chemical repellents to non-target 

species are unknown but are assumed to be similar to the parent chemicals for this risk 

assessment. 

The exposure assessment section evaluates the potential for exposure of humans to the chemical 

repellents WS applies. The exposure assessment begins with the WS use pattern for chemical 

repellents (e.g. problem formulation). An exposure pathway for chemical repellents includes (1) a 

release from a chemical repellent source, (2) an exposure point where human contact can occur, 

and (3) an exposure route such as ingestion, inhalation, or dermal contact by which contact can 

occur. Exposures for the identified human populations are evaluated qualitatively for each 

identified exposure pathway. Risks associated with adverse human health are characterized 

qualitatively in this section. The ecological exposure potential and risk characterization for each 

repellent are also discussed. In cases where data is lacking, USEPA assumes that avian toxicity 

data is representative of reptiles and terrestrial-phase amphibians, and fish toxicity data is 

representative of aquatic-phase amphibians. 

2 AMMONIUM SOAPS OF FATTY ACIDS

2.1 Problem Formulation

2.1.1 Chemical Description and Product Use

Ammonium soaps of fatty acids (CAS number 84776-33-0; synonym: Fatty acids, C8-18 and C18-

unsaturated, ammonium salts and sometimes referred to as ammonium soap salts, ammonium 

soap salts of higher fatty acids or ammonium salts of fatty acids) are a single pesticide active 

ingredient but include multiple C8-18 and C18-unsaturated fatty acids ammonium salts (Table 4) 

(USEPA 2010a;2015a). Most products containing ammonium soaps of fatty acids are comprised 

primarily of shorter-chain saturated fatty acids (ammonium nonanoate and ammonium octanoate) 

(USEPA 2015a). Ammonium soaps of fatty acids is an odor-aversive active ingredient in repellent 

products that can be applied directly to plants, such as nursery stock, ornamentals, flowers, vines, 

shrubs, and trees, to repel deer, rabbits, and other mammals (USEPA 2010a;2015a). Ammonium 

soaps of fatty acids are mildly noticeable to humans but offensive to the olfactory nerve of deer

and are also approved for use on food and feed crops (Andelt et al. 1991, USEPA 2015a, Wagner 

and Nolte 2001). WS uses and distributes products to cooperators containing ammonium soaps 

of fatty acids for deer and rabbit damage protection (Tables 2 and 3). 

Table 4 The chemical name and CAS number for the individual C8- to C18-saturated and C18-unsaturated 

fatty acids ammonium salts within the pesticide active ingredient ammonium soaps of fatty acids (CAS 

Number 84776-33-0). 

Chain length CAS Number Chemical name

Saturated

C8 5972-76-9 Ammonium octanoate or ammonium caprylate

C9 63718-65-0 Ammonium nonanoate
10

C10 16530-70-4 Ammonium decanoate

C11 32582-95-9 Undecanoic acid, ammonium salt

C12 2437-23-2 Ammonium laurate or Dodecanoic acid, ammonium salt

C13 191799-95-8 Tridecanoic acid, ammonium salt

C14 16530-71-5 Ammonium myristate

C15 93917-76-1 Ammonium pentadecanoate

C16 5297-93-8 Ammonium palmitate

C17 94266-36-1 Ammonium heptadecanoate

C18 1002-89-7 Ammonium stearate

Unsaturated

C18 544-60-5 Ammonium oleate

Ammonium soaps of fatty acids is the sole active ingredient in Hinder® (USEPA Registration

Number 5481-508, label version May 6, 2015, AMVAC®) and Hinder®-H Deer & Rabbit Repellent

(USEPA Registration Number 8119-7, label version July 11, 2008, Matson, LLC), which are 

13.8% w/w concentrate products that require dilution before application. It is also the active 

ingredient in Hinder® Deer & Rabbit Repellent (0.66% w/w; USEPA Registration Number 8119-8,

label version February 4, 2010, Matson, LLC), which is a ready-to-use product. These products 

are labeled to limit browsing by white-tailed deer and black-tailed or mule deer on apple and pear 

trees, soybeans, peanuts, carrots, nursery stock, ornamental trees and shrubs, and flowers. 

These products are also labeled to discourage browsing by cottontail rabbits (and other Sylvilagus

spp.) and black-tailed jackrabbits on home gardens and the trunks of nursery stock and 

ornamental trees (USEPA 2015b). They are labeled for terrestrial food and feed crops, such as 

grapes, cereal grains, vegetables, orchards, forage, fodder, and hay (USEPA 2015a). 

Products containing ammonium soaps of fatty acids can be applied by ground equipment or by 

hand with a brush. The application rate for repelling deer on nursery stock and ornamental trees 

and shrubs for the concentrate products is 2–4 gallons of concentrate per 100 gallons of water 

for large applications and 3.2–6.4 fluid ounces per gallon of water for smaller applications (USEPA 

2015b). For repelling rabbits on nursery stock and ornamental trees, the concentrate products are

mixed with equal parts water and applied by brush to trunks of plants, just above the height that 

rabbits might reach. Products containing ammonium soaps of fatty acids should be applied every 

10–14 days for as long as plant protection is needed. Between FY2016 and FY2020, WS used 

Hinder® on an airbase in California to repel an annual average of 8 mule deer browsing 

ornamental plants in the residential area and presenting a human health hazard (Table 1). 

2.1.2 Physical and Chemical Properties

Nonanoic acid, a shorter fatty chain parent and component compound of ammonium nonanoate

is soluble in water and can be a major constituent of some products containing ammonium soaps 

of fatty acids (NIH 2022c, USEPA 2010b;2015a). Given that the longer chain fatty acids of

ammonium soaps of fatty acids are less soluble in water, data on nonanoic acid was often used 

by USEPA as a surrogate for ammonium soaps of fatty acids in their risk assessments (USEPA 

2010a;2015a). Nonanoic acid is an oily liquid with an unpleasant, rancid odor. Nonanoic acid has 

a melting point of 12.3oC and a boiling point of 254.5oC at 760 mm Hg (O'Neil 2001). Nonanoic 

acid has a reported vapor pressure of 1.65 x 10-3 mm Hg at 25oC and a calculated air-water 

partition coefficient (Henry’s Law Constant) of 1.625 x 10-6 atm/m3

/mol at 25oC. Nonanoic acid
11

has a density of 0.9052 grams (g)/milliliter (mL). The water solubility for nonanoic acid is 284

milligrams/Liter (mg/L) at 30oC (NIH 2023a). The estimated Koc for nonanoic acid is from 53 mL/g 

to 111 mL/g. USEPA assumed a value of 100 mL/g is representative of ammonium soaps of fatty 

acids of lengths up to C11-saturated. 

2.1.3 Environmental Fate

Ammonium soaps of fatty acids are slightly soluble in water (USEPA 2010b) with a vapor pressure 

near that of water. They do not readily vaporize or form aerosol particulates (USEPA 2010b). 

Ammonium soaps of fatty acids are expected to degrade rapidly in aerobic soil, primarily via 

microbial action, with a half-life of less than one day (USEPA 2015a). Ammonium soaps of fatty 

acids have the potential to bioaccumulate but are not likely to persist (USEPA 2015a). Ammonium 

soaps of fatty acids readily bind to soil particles (USEPA 2010b). 

2.1.4 Hazard Identification

Ammonium soaps of fatty acids are irritating and corrosive to the eye (USEPA 2012a). When 

applied to human skin for longer periods of time (24 hours), 2.5 milligrams (mg) of ammonium 

soaps of fatty acids can produce mild to moderate irritation (USEPA 2010b). Ammonium soaps 

of fatty acids may also cause allergic skin reactions in some individuals, but the USEPA believes 

allergic reactions are uncommon and transient (USEPA 2010b). 

USEPA reviewed the OPP IDS from 2007-2012 (USEPA 2013a), and no incidents involving 

ammonium soaps of fatty acids were reported.

2.2 Dose-Response Assessment

2.2.1 Human Health Dose-Response

Acute Toxicity

USEPA waived all generic human health toxicity data requirements for soap salts due to the lack 

of effects at high doses (USEPA 2012a). Ammonium soaps of fatty acids are of low acute oral 

and dermal toxicity and have been placed in Toxicity Category IV and III, respectively, for these 

routes of exposure (USEPA 2010b). The acute oral median lethality values (LD50) in the rat is 

>5g/kg-bw, and the acute dermal LD50 is >3 g/kg-bw in the guinea pig (USEPA 2010b). 

Ammonium soaps of fatty acids are not classified as skin sensitizers but may cause allergic skin 

reactions in some individuals. Ammonium soaps of fatty acids are irritating and corrosive to the 

eyes (USEPA 2012a). Information on its acute inhalation toxicity is lacking; however, USEPA 

assumes it will be strongly irritating through the inhalation route because it is an eye and skin 

irritant (USEPA 2010b). 

Subchronic and Chronic Toxicity

Oral dietary exposure of 8 male rats to nonanoic acid at 4.17% in the diet (approximately 2,100 

g/kg-bw/day) for 4 weeks had no effect on survival. A slight 4% decrease in mean growth rate 

was observed but was not statistically significant (USEPA 2004d). 
12

Developmental and Reproductive Effects

No adverse effects occurred in a developmental and maternal toxicity study in rats dosed with 

nonanoic acid (USEPA 2012a). In the study, the no observable adverse effect level (NOAEL) was 

1,500 mg/kg-bw/day, the highest test concentration tested, and the lowest observed adverse 

effect level (LOAEL) was >1,500 mg/kg-bw/day.

Neurotoxicity Effects

A literature review did not identify any reported studies on neurotoxicity effects due to ammonium 

soaps of fatty acids exposure.

Carcinogenicity and Mutagenicity

A study on chronic toxicity/carcinogenicity in mice was conducted for 80 weeks. A dose of 50 mg 

of nonanoic acid (the parent compound of ammonium soaps of fatty acids) was dermally applied 

to each shaved mouse twice a day for 80 weeks. Histopathology showed no non-neoplastic or 

neoplastic lesions on the skins and internal organs of mice (USEPA 2003b). 

Immunotoxicity Effects

A literature review did not identify any reported studies on immunotoxicity effects due to exposure 

of ammonium soaps of fatty acids. 

Endocrine Effects

There is no known evidence that ammonium soaps of fatty acids act as an endocrine disrupter. 

No adverse effects on the endocrine system are known or expected (USEPA 2008d). 

2.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Ammonium soaps of fatty acids are slightly toxic to freshwater fish and freshwater and 

estuarine/marine invertebrates (Table 5) (USEPA 2015a). However, they are practically non-toxic 

to estuarine/marine fish (USEPA 2015a). Freshwater fish are used as a surrogate for aquaticphase amphibians; therefore, ammonium soaps of fatty acids are slightly toxic to aquatic-phase 

amphibians. 

USEPA (2015a) evaluated risks to terrestrial, semi-aquatic, and aquatic plants adjacent to a 

treated field from surface water runoff and spray drift after broadcast application of ammonium 

soaps of fatty acids at 20 pounds a.i./acre and did not find a potential for adverse effects (USEPA 

2015a). 

Table 5 Acute and chronic toxicity to aquatic vertebrates and invertebrates for ammonium soaps of fatty 

acids.

Repellent Test species Test Result 

(mg/L) Reference

Ammonium Soaps of Fatty Acids1
13

Freshwater Fish

Fathead Minnow 

(Pimephales promelas) LC50 104 (USEPA 1992b)

Rainbow Trout

(Oncorhynchus mykiss) LC50 18.06 (USEPA 1992b)

Rainbow Trout 96-hr LC50 12 (USEPA 2015a)

Rainbow Trout NOAEC 

(estimated) 10.3 (USEPA 2015a)

Bluegill Sunfish

(Lepomis macrochirus) LC50 35.35 (USEPA 1992b)

Freshwater 

Invertebrates

Water Flea 

(Daphnia magna)

48-hr EC50 

(immobility) 27 (USEPA 2015a)

Water Flea

NOAEC 

(time to 1st

brood release)

23 (USEPA 2015a)

Estuarine/Marine Fish

Sheepshead Minnow 

(Cyprinodon variegatus) 96-hr LC50 >105 (USEPA 2015a)

Sheepshead Minnow NOAEC 

(estimated) >90 (USEPA 2015a)

Estuarine/Marine 

Invertebrates

Mysid Shrimp 

(Americamysis bahia) 96-hr LC50 67 (USEPA 2015a)

Mysid Shrimp NOAEC 

(estimated) 57 (USEPA 2015a)

Aquatic Plants

Duckweed (Lemna gibba) 7-day EC50

(frond count) 200 (USEPA 2015a)

Duckweed NOAEC 15 (USEPA 2015a)

Green Algae 

(Pseudokirchneriella 

subcapitata)

96-hr EC50 

(cell density) 6.6 (USEPA 2015a)

Green Algae NOAEC 2.9 (USEPA 2015a)

1 Data are for soluble, short-chain (93% C9-saturated) fatty acids. 

Terrestrial Effects Analysis

Ammonium soaps of fatty acids are practically non-toxic to mammals and birds from acute 

exposures (USEPA 2015a) (Table 6). Birds are surrogates for reptiles and terrestrial-phase 

amphibians; therefore, ammonium soap salts are likely practically non-toxic to reptiles and 

terrestrial-phase amphibians. 

Ammonium soaps of fatty acids are practically non-toxic to honeybees, based on acute contact 

tests (48-hr LD50 >100 μg/bee) (USEPA 2015a). 

Chronic toxicity data is unavailable because soap salts undergo rapid degradation in less than 

one day (USEPA 2015a). Mammals (including humans), birds, and invertebrates ingest fatty acids 

as part of their normal daily diet since they are found in lipids in all living tissues, including seeds 

(USEPA 2015a). 

Table 6. Acute oral median lethality and subacute dietary toxicity studies for mammals and birds for 

ammonium soaps of fatty acids.

Test species Test Result Reference

Brown Rat (lab) LD50 >74,000 mg/kg-bw (PMRA 2017)

Bobwhite Quail LD50 2,150 mg/kg-bw (USEPA 1992b)
14

Japanese Quail 8-day dietary LC50

>5,000 mg/kg-diet (practically non-toxic)

or 1,100 mg a.i./kg-diet (USEPA 2015a)

Mallard Duck 8-day dietary LC50 >5,000 mg/kg-diet (practically non-toxic) (USEPA 1992b)

Bobwhite Quail 8-day dietary LC50 >5,000 mg/kg-diet (practically non-toxic) (USEPA 1992b)

Ammonium soaps of fatty acids are phytotoxic (USEPA 2015a), and some registered products 

are intended for use as terrestrial herbicides. Ammonium soaps of fatty acids are more toxic to 

plants when the foliage is exposed to spray drift than by exposure through the roots due to surface 

water runoff (USEPA 2015a). Dicots are more sensitive than monocots (USEPA 2015a). The 

general herbicidal mode of action for ammonium soaps of fatty acids involves the disruption of 

photosynthesis through the destruction of cell membranes resulting in plant death (PMRA 2017). 

2.3 Exposure Assessment and Risk Characterization

2.3.1 Human Health Exposure and Risk Characterization

Exposure to ammonium soaps of fatty acids through dietary exposure is possible; however, the 

unpleasant taste and the ammonia odor would limit oral exposure. Contamination of drinking 

water is unlikely due to ammonium soaps of fatty acids' environmental fate properties and label 

restrictions that make it unlikely for the repellent to reach surface water via runoff or leach into 

groundwater (USEPA 2010b). Ammonium soaps of fatty acids are unlikely to form aerosols due 

to their vapor pressure, making inhalation an unlikely route of exposure (USEPA 2010b). The 

limited uses of ammonium soaps of fatty acids minimize potential exposure. WS does not 

anticipate exposure to the general public. The Hinder® label requires occupational workers to 

wear long-sleeved shirts and pants, chemical-resistant gloves, chemical-resistant footwear, 

socks, and protective eyewear. As such, WS expects minimal dermal, inhalation and eye 

exposure of workers to ammonium soaps of fatty acids. 

USEPA (2012a) concluded that no risks to human health are expected from the use of ammonium 

soaps of fatty acids based on their low toxicity, environmental fate properties, and low exposure 

potential. They also concluded that residues from pesticide uses are not likely to exceed the levels 

of naturally occurring or intentionally added fatty acids in commonly eaten foods (USEPA 2012a). 

WS historical use patterns for ammonium soaps of fatty acids are limited (repelling mule deer); 

however, this does not indicate future use patterns. Should WS increase its use of ammonium 

soaps of fatty acids, this assessment's exposure and risk conclusions would remain the same.

Ammonium soaps of fatty acids are exempt from the requirement of a tolerance for all labeled 

food and feed uses (40 CFR § 180.1284) (USEPA 2012a). 

2.3.2 Ecological Exposure and Risk Characterization

The Hinder® label does not allow applications of the product directly to water, reducing exposure 

to aquatic resources. Aquatic species living in waterways adjacent to or downstream from 

treatment areas may be exposed through surface runoff and spray drift from broadcast 

applications. However, ammonium soaps of fatty acids undergo rapid microbial degradation and 

readily bind to soil which indicates runoff or leaching of significant concentrations of ammonium 

soaps of fatty acids into water bodies is not expected (USEPA 2015a). 
15

Applications of products containing ammonium soaps of fatty acids may expose nontarget birds, 

mammals, reptiles, and the terrestrial stages of amphibians in the treatment area or adjacent to 

the treatment area. USEPA (2015a) reviewed the Ecological Incident Information System (1989–

2012) and did not find reported incidents involving ammonium soaps of fatty acids. In 2012, the 

USEPA (2015a) reviewed the Avian Incident Monitoring System maintained by the American Bird 

Conservancy and did not find incidents involving these products. Ammonium soaps of fatty acids’ 

environmental fate properties, label requirements, the proposed WS use pattern, and the 

favorable toxicity data indicate negligible risk to non-target terrestrial and aquatic species. 

Ammonium soaps of fatty acids can be phytotoxic (some formulations are labeled herbicides). 

The Hinder® label indicates that applications when plants are in bloom, may result in phytotoxicity. 

USEPA (2015a) found it unlikely that the use of products containing ammonium soaps of fatty 

acids would cause direct effects on threatened and endangered Federally listed species. 

3 ANTHRAQUINONE

3.1 Problem Formulation

3.1.1 Chemical Description and Product Use

Anthraquinone (CAS number 84-65-1; synonyms: 9,10-Anthraquinone and anthracene-9,10-

dione) is an aromatic organic compound that occurs naturally in certain insects, fungi, and plants 

such as Senna pods. It is a coloring pigment in organisms and is used commercially to 

manufacture dyes. It has been used medicinally as a natural laxative. For example, the Egyptian 

senna (Senna alexandrina) brewed as tea has been used for its laxative properties. 

Anthraquinone has been used as a bird repellent since the 1940s when German scientists first 

patented it. Many research studies on the repellent efficacy of anthraquinone with various species 

have been published and summarized in a review by Deliberto and Werner (2016). Anthraquinone 

has a long history of use as a bird repellent for geese and may be effective due to post-ingestional 

distress caused by irritation of the gut. It has been shown to be effective for Canada geese on turf

during 7-day tests (Dolbeer et al. 1998). 

Anthraquinone is the active ingredient in Flight Control® Plus (50% w/w; USEPA Registration

Number 69969-1) and Flight Control® Max (18.6% w/w; USEPA Registration Number 69969-7; 

alternate brand names are AV-5055 and AV-1011® Liquid Rice Seed Treatment). The registration 

for Flight Control® Plus was canceled on September 7, 2021. Flight Control® Max contains 18.6%

w/w anthraquinone and 81.4% w/w other ingredients. Other ingredients include limestone (15–

40% w/w) and water (30–60% w/w) (Arkion 2021, USEPA 2022c). WS uses anthraquinone under

the Flight Control® Max label. There are no approved food uses, and no tolerances or tolerance 

exemptions have been established for anthraquinone (USEPA 2022i). 

Although WS only used Flight Control® Plus between FY11 and FY20, WS may use the Flight 

Control® Max product in the future. Flight Control® Max is registered to repel Canada geese from 

turf. Recent label changes to Flight Control® Max restricted the allowed-use sites to areas 

adjacent to or on airport property, commercial sites, industrial sites, cemeteries, landfills, and 

managed waste dumpsites (USEPA 2022c). The maximum single application rate is 1.03 pounds

a.i./acre with a maximum of 7 applications per year and a 14-day minimum retreatment interval.

Under previous labels, WS used Flight Control Plus to protect property composed of parks and 
16

privately managed grass areas. Due to label restrictions, future WS use of anthraquinone will 

mainly be at airports to reduce bird air strike hazards.

An anthraquinone seed-treatment product, Avipel® Liquid Corn Seed Treatment (USEPA 

Registration Number 69969-6), is labeled as a bird repellent for seeds, which is a non-food use.

Avipel® Liquid Corn Seed Treatment contains 13.6% w/w anthraquinone and 86.4% w/w other 

ingredients and is labeled for the treatment of field and sweet corn seed to protect against 

consumption by pheasants, blackbirds, crows, grackles, cowbirds, starlings, and cranes (USEPA 

2021a). WS has not used this product; however, they may recommend it to cooperators.

From FY11 to FY15, WS applied an annual average of 99 gallons of Flight Control® Plus in 45 

work tasks to repel Canada geese (Tables 1 and 2). From FY16 to FY20, WS applied an annual 

average of 48.3 gallons of Flight Control® Plus in 21 work tasks to repel Canada geese (Tables 1 

and 2).

3.1.2 Physical and Chemical Properties

Anthraquinone (C14H8O2) is a light-yellow crystal with an aromatic odor. Anthraquinone has a 

melting point of 286oC and a boiling point of 377oC at 760 mm Hg (European Chemicals Agency 

2019, O'Neil 2001). Anthraquinone has a reported vapor pressure of 1.16 x 10-7 mm Hg at 25oC

and calculated air–water partition coefficient of 2.35 x 10-8 atm/m3

/mol at 25oC suggesting it does 

not volatilize into the air from soil or water. Anthraquinone is moderately soluble in water (1.75 

mg/L). The log octanol-water partition coefficient (Kow) is 3.39 at 25oC, suggesting it may 

bioconcentrate in aquatic organisms (USEPA 2022b). Fish bioaccumulation data is lacking.

However, USEPA estimated the log octanol-air partition coefficient (KOA) as -6.017, which 

suggests anthraquinone may not bioaccumulate in terrestrial organisms (USEPA 2022b). 

3.1.3 Environmental Fate

Anthraquinone breaks down quickly in water in the presence of light with a reported half-life of 

0.0456 days at a neutral pH; but is stable to hydrolysis as it has no hydrolyzable groups. 

Anthraquinone is moderately susceptible to microbial degradation in the presence of soil and 

water. It is moderately persistent in soils with aerobic soil metabolism half-life values ranging from 

59.4 to 86.7 days. The aerobic aquatic metabolism half-life ranges from 28.4 to 34.9 days in water 

and sediment. Anthraquinone is considered slightly mobile in soil based on estimated organiccarbon partition coefficients (Koc) (USEPA 2022b).

3.1.4 Hazard Identification

The mode of action for anthraquinone is not well understood, but its post-ingestive effects are 

likely responsible for subsequent feeding repellency. The emetic response is produced through 

irritation of the gut, but the actual mechanism is unclear. The post-ingestive distress that occurs 

after eating anthraquinone-treated food results in a conditioned avoidance of that food type 

(DeLiberto and Werner 2016).

Humans can be exposed to anthraquinone in food, drinking water, and applicators through 

occupational exposure (USEPA 2022i). When ingested, anthraquinone is slowly distributed to 

tissues and slowly metabolized and excreted via a saturable kinetic process (USEPA 2022i). 
17

Females may have slower clearance and metabolism than males and, therefore, can have higher 

tissue concentrations (USEPA 2022i). 

No serious side effects or adverse effects have been reported with the use of anthraquinone when 

used for medicinal use. Patients may experience irritability, difficulty sleeping, confusion, 

nightmares, mood swings, depression, and suffer from delusions and suicidal thoughts in cases 

where an excess dose is taken. The liver, kidneys, and thyroid are the primary organs affected 

by repeated exposure to anthraquinone (USEPA 2022i). 

No adverse incidents from anthraquinone use have been reported in the OPP IDS and the CDC

and Prevention/National Institute for Occupational Safety and Health (CDC/NIOSH) Sentinel 

Event Notification System for Occupational Risk-Pesticides (SENSOR) database. The reporting 

period for the IDS database was from January 1, 2016, through July 14, 2021. The reporting 

period for the SENSOR database was 1998-2017 (USEPA 2022i). USEPA has not established 

any tolerances for anthraquinone use. USEPA did estimate a chronic population-adjusted dose 

(cPAD) of 0.03 mg/kg-bw/day that was derived from the LOAEL (25 mg/kg-bw/day) (USEPA 

2022i). The cPAD is equivalent to a chronic reference dose. An acute reference dose was not 

estimated.

3.2 Dose-Response Assessment

3.2.1 Human Health Dose-Response

Acute Toxicity

Acute median lethality (LD50) values suggest that anthraquinone has low mammalian acute 

toxicity via oral, dermal, and inhalation exposure routes (Table 7). The eye and dermal irritation 

studies show that anthraquinone is a slight irritant to the skin and eyes when using rabbits as a 

test species (Toxicity Category III). The dermal sensitization study shows that anthraquinone is 

not a skin sensitizer in guinea pigs. The Safety Data Sheet for Flight Control® Max (18.6% w/w 

anthraquinone) reports that the formulation is a moderate eye irritant and a slight skin irritant 

(Arkion 2021). Acute toxicity is similar between technical anthraquinone (99% w/w) and the 18.6% 

w/w end-use formulation that WS may use in the future. 

Table 7 Acute oral median lethality studies for mammals for technical anthraquinone and an end-use 

product.

Test Species Test

Result 

(Anthraquinone 

97–99% w/w)

Result 

(Flight Control®

Max, 18.6% w/w)

USEPA 

Toxicity 

Category

Laboratory Brown Rat Acute Oral LD50 >5,143 mg/kg/bw >5,000 mg/kg-bw IV

Domestic Rabbit Acute Dermal LD50 >5,000 mg/kg-bw >5,000 mg/kg-bw IV

Laboratory Brown Rat Acute Inhalation LC50 >2.14 mg/L >2.04 mg/L IV

Domestic Rabbit Primary Dermal Irritation Slight Slight IV

Domestic Rabbit Primary Eye Irritation Mild Moderate IV and III

Mouse Skin Sensitizer No - NA

Guinea Pig (Cavia 

porcellus) Skin Sensitizer - Not a sensitizer NA

NA = Not applicable
18

References: (Arkion 2021, USEPA 2022i)

Subchronic and Chronic Toxicity

Subchronic short-term (30 days) and intermediate-term (13 weeks) dietary exposure and chronic 

(105 weeks) dietary studies are available (USEPA 2022i). In the subchronic oral toxicity study,

male/female (M/F) rats were exposed to 0/0, 40/44, 125/150, or 495/661 mg/kg-bw/day for 30 

days and then the 40/44 mg/kg-bw/day dose level was lowered to 11/16 mg/kg-bw/day (M/F) for 

weeks 5–13 weeks. Various physiological endpoints were assessed, including neurological, liver, 

kidney, hematological, and thyroid impacts at the different dose levels in male and female rats. 

Some impacts were noted in liver, hematological, thyroid, adrenal, and kidney endpoints but were 

not observed in a dose-dependent manner or were not considered adverse. The LOAEL for these 

studies was 44 mg/kg-bw/day, the lowest dose tested, based on a decrease in body weight in 

female rats.

A combined chronic dietary and carcinogenicity study is available for anthraquinone, where rats 

were exposed for 105 weeks to either 0/0, 20/25, 45/50, 90/100, or 180/200 mg/kg-bw/day (M/F)

by dietary exposure. There were no effects of any dose on mortality, clinical signs, or food 

consumption. Plasma concentrations were approximately 2 to 3-fold in female rats compared to 

males, which is reflected in the difference in effects that were noted in female rats compared to 

male rats during the study. A NOAEL was not established for either sex since the LOAEL was the 

lowest test concentration tested (20/25 mg/kg-bw/day, M/F). The LOAEL was based on a 

decrease in body weights and kidney and liver histopathological effects in male and female rats 

(USEPA 2022i).

Developmental and Reproductive Effects

Two studies are available that evaluate developmental effects. In a rat study, pregnant female 

rats were administered technical anthraquinone by oral gavage at doses of 0, 10, 50, or 150 

mg/kg-bw/day on gestation days 6 through 19 (USEPA 2022i). The maternal NOAEL was 50 

mg/kg-bw/day, and the LOAEL was 150 mg/kg-bw/day based on decreased body weight and food 

consumption. The developmental NOAEL and the LOAEL were the same as the maternal values 

and were based on decreased fetal, litter, and placental weight. In the rabbit study, pregnant 

rabbits were dosed at 0, 25, 50, or 100 mg/kg-bw/day from gestation days 6 through 28. The 

maternal NOAEL was 25 mg/kg-bw/day, and the LOAEL was 50 mg/kg-bw/day based on 

increased mortality, late abortions, and clinical signs such as decreased feces output and red 

urine. The developmental NOAEL and LOAEL were the same based on late abortions.

USEPA waived the reproductive study that is associated with pesticide registration (USEPA 

2022i). However, in the subchronic oral toxicity study in rats, adverse changes to the reproductive 

tract of females were noted at the highest test concentration tested, 495 mg/kg-bw/day. This 

included effects on the ovaries, vagina, and uterus in dosed rats. In another subchronic study 

using rats, there was a dose-dependent increase in estrous cycle length at doses equal to or 

greater than 1,130 mg/kg-bw/day.
19

Neurotoxicity Effects

A literature review did not identify any reported studies on neurotoxicity effects due to 

anthraquinone exposure. USEPA (2022i) waived acute and subchronic neurotoxicity studies for 

anthraquinone. Neurotoxicity is not expected to be a sensitive endpoint compared to other 

endpoints. Available subchronic toxicity data in the rat study shows a lack of effects on 

neurohistopathology and neurological parameters.

Carcinogenicity and Mutagenicity

A review of a combined chronic and carcinogenicity study in rats at 0/0, 20/25, 45/50, 95/100, and 

180/200 mg/kg-bw/day (M/F) by dietary exposure conducted by the USEPA OPP Health Effects 

Division (HED), Cancer Assessment Review Committee (CARC) determined that kidney tumors 

observed in female rats at 50, 100, and 200 mg/kg-bw/day were determined to be treatmentrelated (USEPA 2022i). However, urinary and bladder kidney tumors observed at the highest test 

concentration in male rats were not treatment-related. The CARC determined that thyroid tumors 

observed at the various doses in female rats were also not treatment-related.

In a second carcinogenicity study, male/female mice were exposed to dietary concentrations of

(0/0, 90/80, 265/235, or 825/745 mg/kg-bw/day) for 105 weeks. No effects on clinical symptoms 

and food consumption were noted in either sex. The LOAEL was 90/80 mg/kg-bw/day (M/F), the 

lowest dose tested, based on histopathology impacts related to centrilobular hypertrophy in the 

liver. A NOAEL was not established. A review by the CARC determined that liver and thyroid 

tumors observed during the study were treatment-related. The incidence of liver carcinomas was 

significant at dose levels of 265/235 and 825/745 mg/kg-bw/day (M/F); the incidence of thyroid 

carcinomas was significant at the highest dose level tested (USEPA 2022i).

Based on these study results and mutagenicity data showing that the major metabolite of 

anthraquinone, 2-hydroxyanthraquinone, is mutagenic, USEPA currently classifies anthraquinone 

as “Likely to be Carcinogenic to Humans” (USEPA 2022i).

Immunotoxicity Effects

Female mice were administered technical anthraquinone at either 0, 98, 373, or 1245 mg/kgbw/day by dietary exposure for 4 weeks in an immunotoxicity study. No significant effects were 

seen at any concentration on clinical signs, body weights, mortality, body weight gains, food 

consumption, or organ (thymus, spleen, and brain) weights. Anti-sheep red blood cell (SRBC)

plaque-forming assays (PFC) were measured using splenocyte suspensions from each mouse. 

The NOAEL for anti-SRBC PFC response was 1,245 mg/kg-bw/day, and the LOAEL was greater 

than 1,245 mg/kg-bw/day, suggesting that anthraquinone is not an immunotoxic chemical

(USEPA 2022i).

Endocrine Effects

In the subchronic dietary toxicity study (30 days and 13 weeks), male/female (M/F) rats were 

exposed to technical anthraquinone at 0/0, 40/44, 125/150, or 495/661 mg/kg-bw/day for 30 days 

and then the 40/44 mg/kg-bw/day dose level was lowered to 11/16 mg/kg-bw/day (M/F) for weeks 

5–13. Thyroid follicular cell hypertrophy was observed in male rats at ≥125 mg/kg-bw/day, with 
20

the incidence and severity increasing in a dose-dependent manner. There was an increase in 

thyroid weight in males fed 495 mg/kg-bw/day. Thyroid follicular cell hypertrophy was not 

observed in female rats; however, increased thyroid weights were noted but were not dosedependent. There were impacts on adrenal gland weights and histology in female rats at 

concentrations ≥150 mg/kg-bw/day (USEPA 2022i). The resulting LOAEL in the study (44 mg/kgbw/day) was based on decreased body weights in female rats.

In another study, Sprague-Dawley rats were dermally exposed daily for 28 days to technical 

anthraquinone at dose levels of 0, 100, 300, or 1000 mg/kg-bw/day. The LOAEL was 1,000 mg/kgbw/day based on thyroid follicular cell hypertrophy. The NOAEL was 300 mg/kg-bw/day. 

3.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Anthraquinone has low toxicity to fish based on available data. The acute toxicity of anthraquinone 

to aquatic invertebrates is variable. The freshwater cladoceran, Daphnia magna, appears to be 

the least sensitive aquatic invertebrate to anthraquinone; however, it is highly toxic to the marine 

mysid shrimp, Mysidopsis bahia, the freshwater scud (Hyallela azteca) and midge larvae 

(Chironomus tentans) (Table 8).

Table 8. Acute and chronic toxicity to aquatic vertebrates and invertebrates for anthraquinone.

Taxonomic 

group Test species Test Result (mg/L) Reference

Freshwater Fish

Bluegill Sunfish (Lepomis 

macrochirus) LC50 >5 (Verschueren 2001)

Bluegill Sunfish 96-hr LC50 >0.190 (USEPA 2022b)

Fathead Minnow (Pimephales 

promelas) LC50 2,650 (Verschueren 2001)

Rainbow Trout

(Oncorhynchus mykiss) 96-hr LC50 >0.150 (USEPA 2022b)

Freshwater 

Invertebrates

Water Flea (Daphnia magna) 48-hr EC50 >0.240 (USEPA 2022b)

Scud (Hyallela azteca) 96-hr EC50 0.338 (USEPA 2022b)

Midge (Chironomus tentans) 14-day 

NOAEC 0.058 (USEPA 2022b)

Estuarine/Marine 

Invertebrates

Mysid Shrimp (Mysidopsis 

bahia) 48-hr LC50 0.0942 (USEPA 2022b)

Eastern Oyster 

(Crassostrea virginica) 96-hr EC50 >0.017 (USEPA 2022b)

Anthraquinone toxicity to aquatic vascular plants and algae is low based on available data. The 

8-day EC50 for Lemna minor is 0.500 mg/L, while the 5-day EC50 for the green algae, Raphidocelis 

subcapitata, was reported as greater than 20.8 mg/L (Mallakin et al. 1999, Schrader et al. 1998). 

Anthraquinone is toxic to the cyanobacterium, Oscillatoria chalybea, with a reported 5-day median 

inhibition concentration (IC50) of 0.0208 mg/L (Schrader et al. 1998). 
21

Terrestrial Effects Analysis

Anthraquinone contact toxicity to honeybees (Apis mellifera) is low, with a reported LD50 greater 

than 0.025 mg a.i./bee (USEPA 2022b). There are no data available on the phytotoxicity of 

anthraquinone to terrestrial plants. Anthraquinone is considered practically non-toxic to birds and 

mammals in acute exposures (Table 9). Sublethal effects from subchronic dietary exposures to 

rats at the LOAEC included weight loss (USEPA 2022b). USEPA (2022b) reported that in the 

bobwhite quail acute oral toxicity study, the LD50 was greater than 2,000 mg/kg-bw in a limit test, 

suggesting it is practically non-toxic to birds on an acute basis. Mortalities were observed at 2,000 

and 3,000 mg/kg-bw, with sublethal effects noted in all three treatment groups of 1,000, 2,000, 

and 3,000 mg/kg-bw. Sublethal effects noted in acute exposures include hypoactivity, emaciation, 

moribundity, and reduced body weight (USEPA 2022b). 

Table 9. Acute oral median lethality and subacute dietary toxicity studies for mammals and birds for 

anthraquinone.

Test species Test Result Reference

Brown Rat (lab)

LD50 >5,143 mg/kg-bw (USEPA 2022i)

90-day NOAEC 

and LOAEC 11 mg/kg-bw and 40 mg/kg-bw (USEPA 2022i)

Mouse LD50 >5,000 mg/kg-bw (USEPA 1998a)

Bobwhite Quail LD50 >2,000 mg/kg-bw (USEPA 2022b)

3.3 Exposure Assessment and Risk Characterization

3.3.1 Human Health Exposure and Risk Characterization

WS's use of anthraquinone products in the future will be limited to repelling geese at labelapproved locations, including on and around airport properties. The recent label changes to Flight 

Control® Max that restrict use at other turf use sites suggest exposure to the public, including 

children, will be low for all anthraquinone uses by WS. Anthraquinone use by WS will not result in 

residues on food items. Estimates of residues that could occur in drinking water for current and 

past uses suggest that drinking water is not a significant exposure pathway. USEPA (2022i)

estimated drinking water residues of anthraquinone for a range of uses and, in an aggregate risk 

analysis, determined that current uses of anthraquinone will not result in risks to the public. 

USEPA evaluated the risk to the public from residential turf applications which were recently 

canceled (USEPA 2022i). Exposure assumptions for residential turf use are highly conservative 

when compared to the exposure assumptions that would occur from anthraquinone use on turf at 

airports. The frequency of access by the public to residential turf would be much greater than 

what would occur at airports, where access to treatment areas would be restricted due to safety 

concerns. Regardless the residential turf uses did not result in a risk to the public, including 

children in acute and chronic exposures. These risks would be negligible in airport settings where 

WS uses anthraquinone products.

Exposure and risks to human health are greatest for workers who apply anthraquinone. Recent 

changes to the label regarding Personal Protective Equipment (PPE) reduce the potential risk to 

workers who apply anthraquinone. Current PPE requirements for all anthraquinone uses include 

long-sleeved shirts and pants, shoes and socks, chemical-resistant gloves, protective goggles, 
22

and NIOSH-approved particulate filter facepiece respirator with an N, R, or P filter (USEPA 

2022c). Recent risk assessments that evaluated cancer and non-cancer risk to workers during 

and after the application of anthraquinone did not identify significant risks to workers following 

these PPE requirements (USEPA 2022i). Occupational risks were estimated for both inhalation 

and dermal exposure pathways.

3.3.2 Ecological Exposure and Risk Characterization

Label restrictions for anthraquinone will reduce the potential for runoff and drift during application. 

The label states that applications should not be made when the surface to be treated is wet, or 

rain is expected. The formulation also contains a sticking adjuvant that allows the product to 

adhere more effectively to turf, reducing the chances of washing off during a rain event after 

application. The label also states to avoid applications during windy conditions reducing the 

potential for offsite drift. 

Recent environmental fate modeling conducted by USEPA estimated peak and 21-day surface 

water concentrations of 12.2 and 3.4 μg/L, respectively. The estimates were based on maximum 

turf use rates applied seven times every 14 days. Rainfall patterns and soil types in Florida and 

Pennsylvania were used as representative use sites in the modeling scenario (USEPA 2022b).

The maximum estimated surface water concentrations were compared to the available effects 

data to determine the potential risk to non-target aquatic vertebrates, aquatic invertebrates, and 

aquatic plants. No levels of concern were exceeded for non-listed (species not listed as 

threatened or endangered) freshwater vertebrates, invertebrates, or aquatic plants. The 

screening level risk assessment suggests negligible risks to aquatic biota under maximum labeled 

use rates. Low rates or less frequent applications would lower the risk to non-target aquatic 

organisms.

Exposure of terrestrial non-target organisms to anthraquinone is anticipated to occur primarily for 

those species that occur at use sites which consist of developed areas such as areas adjacent to 

or on airport property, commercial and industrial sites, cemeteries, and landfills, and managed 

waste dumpsites. Applications are only allowed to turf on these sites to repel geese, reducing 

exposure to terrestrial non-target organisms. Exposure would be greatest for those animals that 

consume turf after anthraquinone application. Mammals and birds that forage on treated turf 

would have the greatest potential for dietary exposure. Although previous use of anthraquinone 

by WS included turf applications, current WS use of anthraquinone is on turf at airports that are 

highly managed and disturbed areas where non-target terrestrial vertebrates and invertebrates 

would not be expected to use for foraging or nesting habitat.

USEPA recently prepared a terrestrial risk assessment characterizing the risks of anthraquinone 

to non-target birds, amphibians, and mammals under various use scenarios (USEPA 2022b). For 

turf, the WS use pattern, the highest maximum application rate, and application frequency were 

used to estimate residues that could occur on forage items for non-target terrestrial vertebrates. 

Anthraquinone residues were estimated using the USEPA Terrestrial Exposure Model (T-REX). 

Maximum residues ranged from highest on short and long grass, ranging from 54.6 mg/kg for 

seed pods and fruit to 874 mg/kg for short grass. These values represent residues that would 

occur if directly treated with anthraquinone. 
23

The estimated residues were compared to the available effects data for anthraquinone to 

determine if there is a risk to non-target terrestrial vertebrates. The risk assessment concluded 

that the risk to non-target birds, amphibians, and mammals did not exceed USEPA levels of 

concern, suggesting a negligible risk to non-target vertebrate species from anthraquinone use by 

WS. Risks are also not anticipated for terrestrial invertebrates based on the available toxicity data 

for honeybees. There is uncertainty regarding risks to non-target terrestrial plants due to a lack of 

toxicity data. No reports of adverse effects on target or non-target plants have been reported 

suggesting that risks are low. In addition, the use sites for anthraquinone are highly managed 

areas where diverse terrestrial plant life is not expected to be present.

4 CAPSAICIN

4.1 Problem Formulation

4.1.1 Chemical Description and Product Use

Capsaicin and related capsaicinoids (CAS number 404-86-4) are naturally occurring chemical 

compounds found in edible fruits of the genus Capsicum. Capsaicin is regulated as a biopesticide 

or biochemical active ingredient (USEPA 2010e). The products used to repel animals have a low 

concentration of capsaicin, ranging from 0.001% to 2.5% w/w, and are unlikely to result in harm 

to the general population (USEPA 2022e). Capsaicin is registered for use in liquid sprays to apply 

directly to plants to repel mammalian herbivores such as voles, deer, rabbits, and squirrels. 

Capsaicin is also used in a gel on roosting structures (0.04% w/w capsaicin) for pigeons to keep 

them from landing and as an aerosol spray for predators that may attack humans (1–2.5% w/w 

capsaicin) (USEPA 2022e). 

As a plant repellent, it makes the vegetation distasteful to mammalian herbivores. Animals 

attempting to eat treated plant material are not harmed, but the hot sensation in their mouth or 

throat will discourage further feeding. For predators, it is formulated into a spray, “pepper spray,” 

which sprays bursts of atomized capsaicin that spread up to 25 feet. Inhalation results in the 

swelling of nasal and lung membranes and eye exposure causing temporary blindness and

general discomfort. Capsaicin is also an active ingredient in some products containing egg solids,

which are used to repel white-tailed deer and other mammal target species; the active ingredient 

of egg solids is covered elsewhere in this risk assessment.

WS makes ground applications of repellent products containing capsaicin to plant foliage to deter 

herbivores from browsing. WS employees in areas with active bears may carry bear repellents 

containing capsaicin to protect themselves from a potential bear attack. 

4.1.2 Physical and Chemical Properties

Capsaicin (C18H27NO3) is a white crystalline powder or dark red to orange solid or liquid (NCBI 

2022b, USEPA 2009b;2010e). It is practically insoluble in water. It has a pungent odor (USEPA 

2010e).

4.1.3 Environmental Fate
24

Capsaicin rapidly breaks down and is not persistent in the environment (USEPA 2009a). 

Capsaicin degrades rapidly in soils, with a half-life ranging from 2 to 8 days, and is metabolized 

by bacteria in soil (USEPA 2010e).

4.1.4 Hazard Identification

Capsaicin is classified as “generally recognized as safe” (GRAS) when used as a food additive. 

Capsaicin is also exempt from the requirement of a tolerance in or on all food commodities when 

used as a pesticide active ingredient in accordance with approved label rates and good 

agricultural practices (USEPA 2009a;2010e).

USEPA reviewed the Incident Data System, and 5 of the 9 incidents reported were attributed to 

bear and dog repellents, mostly due to a lack of efficacy. One incident occurred with a red pepper 

spray, but the information was lacking on the cause. Two incidents were from misuse or not 

following label instructions. One incident was considered minor and caused minor irritation to the 

throat and eyes; however, USEPA did not specify the product or formulation associated with the 

report (USEPA 2009a).

USEPA waived data requirements for the 90-day oral toxicity, prenatal development, and 

mutagenicity studies due to capsaicin’s use as a food additive without adverse impacts on human 

health (USEPA 2009a). USEPA evaluated one study that found capsaicin weakly mutagenic at 

the highest dose tested and concluded no harm to human health would occur when repellent 

products containing capsaicin are used according to label instructions (USEPA 2009e). USEPA 

considered the history of capsaicin used in food with no observed effect, the low concentration of 

capsaicin in repellent products, and its rapid degradation in the environment (USEPA 2009e). 

4.2 Dose-Response Assessment

4.2.1 Human Health Dose-Response

Acute Toxicity

Capsaicin is non-toxic to mammals based on acute oral and dermal toxicity studies. A 2.5% w/w 

capsaicin product’s LD50 was >5,000 mg/kg-bw, Toxicity Category IV, for both oral and dermal 

exposures. Acute inhalation toxicity for a product containing 2.5% w/w capsaicin is Toxicity 

Category III. It is virtually non-toxic through the inhalation route of exposure, but direct inhalation 

of defensive sprays can cause temporary coughing and breathing discomfort, which dissipates 

rapidly within 3 to 15 minutes with no long-term effects (USEPA 2010e). The 2.5% w/w capsaicin 

substance was not considered an eye or dermal irritant (Toxicity Category IV for both) and was 

not a dermal sensitizer (USEPA 2009c). However, direct eye and skin contact with defensive 

sprays will cause eye discomfort and even temporary blindness and a temporary burning 

sensation of the skin (USEPA 2010e).

Subchronic and Chronic Toxicity, Developmental Toxicity, Mutagenicity, Immunotoxicity

USEPA waived the requirements for subchronic and developmental toxicity, mutagenicity, 

immunotoxicity, and chronic testing for capsaicin due to its lack of acute toxicity and use as a food 

additive. USEPA reviewed one study where capsaicin was weakly mutagenic at the highest dose 
25

tested; upon further review, USEPA found it unlikely capsaicin will cause mutagenic effects when 

repellent products are used according to label instructions (USEPA 2009a;e). 

4.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Capsaicin is non-toxic and does not persist in the environment, indicating minimal risks to all nontarget organisms. As such, the USEPA (2009c) waived the tier I ecotoxicity data requirements for 

capsaicin.

Terrestrial Effects Analysis

USEPA waived capsaicin’s ecotoxicity data requirements for terrestrial species because of its low 

hazard and risk to the environment (USEPA 2009c). USEPA assumes that terrestrial species 

would avoid exposure to capsaicin because it is a fast-acting irritant when consumed or exposed 

to the skin, resulting in minimal risk to these species. 

4.3 Exposure Assessment and Risk Characterization

4.3.1 Human Health Exposure and Risk Characterization

WS does not expect an exposure risk to the general public through its use of capsaicin repellents. 

WS uses repellents containing capsaicin to prevent mammals from browsing vegetation. It may 

carry capsaicin-containing repellent to protect them from potentially human-threatening animals 

as they work in the field (e.g., bear spray in grizzly bear habitat). Dietary exposure through 

capsaicin residues on food and drinking water is not expected. Consumption of capsaicin is a 

regular part of the human diet and is not associated with deleterious effects (USEPA 2010e). The 

product labels do not allow applications to water resources, and capsaicin’s environmental fate 

properties indicate runoff and leaching into water resources is unlikely. WS makes ground 

applications and does not expect exposure to the general public due to spray drift.

Capsaicin can cause slight eye and skin irritation. Several product labels with capsaicin listed as 

an active ingredient require PPE to protect the hands and face and to prevent dermal exposure 

and protective language to reduce potential exposure to workers (USEPA 2022e). Capsaicin’s 

environmental fate properties indicate human exposure to residues is expected to be minimal 

(USEPA 2009a). USEPA (2009a) reviewed the Incident Data System (date range not provided). 

Of the nine reports involving capsaicin, one caused minor irritation to the throat and eyes; 

however, information was lacking to determine if this was from product misuse. The other 

incidents involved misuse, not following label directions, or the repellent not working as expected 

against bears and dogs. None were occupational exposures (USEPA 2010e) and none involved 

WS. 

WS use pattern for repellent products containing capsaicin and capsaicin’s environmental fate 

properties, label language, and favorable toxicity profile indicates a negligible risk to the general 

public and WS applicators.

4.3.2 Ecological Exposure and Risk Characterization
26

The labels for repellent products containing capsaicin do not allow applications to water 

resources, which reduces aquatic exposure risk. The rapid breakdown of capsaicin in the 

environment indicates runoff or leaching into water resources would be minimal.

Capsaicin's low-use volumes, biodegradability, and lack of persistence in the environment 

(minimal residue exposure) indicate minimal exposure risk to terrestrial species. Capsaicin acts 

as a repellent, and mammals sensitive to it would stop browsing on foliage treated with repellents 

containing capsaicin.

WS finds capsaicin is not expected to have adverse effects on non-target terrestrial and aquatic 

species due to its favorable toxicity profile, environmental fate, label requirements, and WS use 

patterns. The USEPA (2009c) concluded the same findings. Capsaicin is non-toxic and does not 

persist in the environment, indicating minimal risks to all non-target organisms (USEPA 2009c). 

5 EGG SOLIDS

5.1 Problem Formulation

5.1.1 Chemical Description and Product Use

Egg solids (CAS number 51609-52-0; synonym: putrescent whole egg solids) are simply dried 

chicken eggs that have been pasteurized and are free of viable pathogens (USEPA 2018c). Egg 

solids are found in several registered pesticide formulations to repel mammals, primarily from 

feeding on vegetation by an aversive odor and taste (USEPA 2018c). The FDA considers egg 

solids as a GRAS chemical when it is used as a food additive. The USEPA classified egg solids 

as a biopesticide or biochemical pesticide active ingredient (USEPA 2018c). Putrescent whole 

egg solids (same CAS number) are also included in the list of allowed MRP active ingredients in 

40CFR 152.25(f). MRP products containing putrescent whole egg solids are covered in another 

Risk Assessment. 

Pesticide products containing egg solids as the active ingredient are registered for use in home 

gardens, nurseries, greenhouses, and forestry plantations, on various fruit and nut trees, and on 

ornamental woody shrubs (USEPA 2018c). Applications are applied in dust and liquid forms 

(USEPA 2018c). Products containing egg solids can be used before and after flowering. USEPA 

has established a tolerance exemption for egg solids for pesticide food uses in accordance with 

the criteria specified in 40 CFR 180.1071. However, product labels for repellent products do not 

allow for use on or drift onto plant parts intended for human consumption because the proteins in 

egg solids may cause allergic reactions in some people (USEPA 2018c;2022h). 

Some registered products containing egg solids include other active ingredients in their 

formulation, including capsaicin and garlic oil. Capsaicin and garlic oil also have repellent 

properties and are covered separately in this assessment. 

5.1.2 Physical and Chemical Properties

Egg solids are a light brown to beige powder with a malty odor (USEPA 2011c). They are

practically insoluble in water (USEPA 2011b). 

5.1.3 Environmental Fate
27

Egg solids are organic matter that rapidly degrades (decomposes) in the environment and are

expected to be non-persistent (USEPA 1992a).

5.1.4 Hazard Identification

Egg solids are non-toxic to humans and are classified as a biopesticide by EPA and GRAS by 

FDA when used as a food additive (USEPA 1992a;2018c). USEPA waived most of the data 

requirements for the reregistration of pesticide products containing egg solids, including data for 

toxicology, residue chemistry, human exposure, and ecological effects and environmental fate

(USEPA 2011f).

Egg solids' odor and taste act as a repellent when applied to plants that repel white-tailed deer 

and other target animals from foraging (USEPA 2018c). The target mammals are sensitive to the 

smell and taste of egg solids; however, the odor is barely detectable to humans (USEPA 2018c).

Between April 1, 1996, and March 30, 2016, there were 32 human health-related incidents 

involving accidental ingestion resulting in nausea, inhalation exposures, and eye exposures

resulting in eye irritation in the National Pesticide Information Center (NPIC) (Baker and Grant 

2018). USEPA (2018c) reviewed the Incident Data System and found one incident report of a 

person that experienced discomfort after inhaling a product containing egg solids, which was 

deemed a misuse of the product.

5.2 Dose-Response Assessment

5.2.1 Human Health Dose Response

Acute Toxicity

Egg solids are practically non-toxic on an acute oral, dermal, and inhalation basis (Toxicity 

Category IV for all exposures) (USEPA 2011c). The LD50 values for acute oral and dermal toxicity

are >5,000 mg/kg-bw (Toxicity Category IV) (USEPA 2011f). The acute inhalation LC50 is >2.10 

mg/L (USEPA 2011f). In acute eye irritation studies, egg solids caused corneal irritation, which 

cleared within 48 hours (Toxicity Category III) (USEPA 2011c). Egg solids are a slight dermal 

irritant (Toxicity Category IV) (USEPA 2011c) and may be a skin sensitizer (USEPA 2011c).

Subchronic and Chronic Toxicity

Data is not available on the subchronic and chronic toxicity of egg solids. USEPA waived these 

studies due to the lack of acute toxicity.

Developmental and Reproductive Toxicity, Neurotoxicity Effects, Carcinogenicity and 

Mutagenicity, Immunotoxicity Effects, Endocrine Effects

USEPA waived these studies due to the lack of acute toxicity. There are no reports of adverse 

effects submitted to the USEPA, and it is not expected to have adverse effects on humans

(USEPA 1992a;2011f).

5.2.2 Ecological Effects Dose-Response
28

Aquatic Effects Analysis

USEPA waived the ecotoxicity data requirements for aquatic species for egg solids because of 

their low hazard and risk to the environment (USEPA 2011e). 

Terrestrial Effects Analysis

USEPA waived the ecotoxicity data requirements for terrestrial species because of the low hazard 

and risk to the environment from egg solids (USEPA 2011e). USEPA (2011e) concluded egg 

solids would not result in a hazard or toxic risk to non-target organisms. 

USEPA (2018c) reviewed the Incident Data System for reported incidents and determined it 

unlikely that egg solids used according to their labels would not cause adverse effects on the 

environment. Four incidents involved dogs ingesting small amounts of the product, with some 

experiencing diarrhea and vomiting. Four incidents reported plant damage. From the incidents 

reported to NPIC between April 1, 1996, and March 30, 2016, accidental ingestion was the main 

exposure route, with some of the exposed animals vomiting; however, many reported no 

symptoms (Baker and Grant 2018). 

5.3 Exposure Assessment and Risk Characterization

5.3.1 Human Health Exposure and Risk Characterization

The product labels for repellents containing egg solids do not allow applications or drift to plant 

parts meant for human consumption. This limits exposure through dietary consumption; egg solids 

may cause an allergic reaction in some people. The labels for registered products containing egg 

solids do not require PPE. 

USEPA (2011f;2018c) concluded that applications of products containing egg solids as the active 

ingredient according to label instructions would not result in harm to the general population or 

applicators. Similarly, products containing egg solids that also contain capsaicin and/or garlic oil 

will not result in harm to people (USEPA 2009a). 

5.3.2 Ecological Exposure and Risk Characterization

The labels for registered products containing egg solids do not allow applications to water 

resources, which reduces aquatic exposure risk. Egg solids break down rapidly in the 

environment, indicating runoff and leaching into water resources would be minimal. WS expects 

aquatic exposure to egg solids from its program applications will be negligible.

USEPA (2011e) concluded egg solids would not result in a hazard or toxic risk to non-target 

organisms. The lack of toxicity and the environmental fate properties for egg solids, WS use 

patterns, and the product label requirements indicate WS use of registered products containing 

egg solids will not harm non-target terrestrial and aquatic species.

6 GARLIC OIL

6.1 Problem Formulation

6.1.1 Chemical Description and Product Use
29

Garlic oil (CAS number 8000-78-0) is a naturally occurring oil extract from the bulb and other parts 

of the garlic plant (Allium sativum). Garlic oil is a volatile and strongly scented oil that works to 

deter and prevent the feeding of some species of mammals (including squirrels, rabbits, and deer) 

(USEPA 2022a). The end-use products used to repel animals have concentrations of garlic oil 

ranging from 0.001 to 0.12% w/w active ingredient. Garlic oil is currently registered as an active 

ingredient in 18 products (USEPA 2022a). The labels for these products interchangeably list the 

active ingredient as Garlic oil, Garlic juice, Garlic water, or Garlic. All products are water-based 

compounds with an extract of A. sativum or powder. USEPA considers all such variations of A.

sativum to be Garlic oil under the Pesticide Chemical (PC) Code 128827 (USEPA 2010f). Garlic 

oil is an active ingredient in some products also containing egg solids, which are used to repel 

white-tailed deer and other mammal target species; the active ingredient of egg solids is covered 

elsewhere in this risk assessment. Garlic and garlic oil are also included in the list of allowed MRP 

active ingredients in 40CFR 152.25(f). MRP products containing garlic and garlic oil are covered 

in another Risk Assessment.

WS may use and distribute products containing garlic oil to cooperators to deter herbivores from 

browsing.

6.1.2 Physical and Chemical Properties

Garlic oil is a light tan to dark green liquid or powder (USEPA 2009f;2022a). It has a pungent odor

and is partial to fully soluble in water (USEPA 2009f;2022a).

6.1.3 Environmental Fate

Garlic oil biodegrades rapidly and has low to no persistence in the environment (USEPA 2022a).

6.1.4 Hazard Identification

Garlic oil is classified as GRAS when used as a food additive. Garlic oil is also exempt from the 

requirement of a tolerance in or on all food commodities when used as a pesticide active 

ingredient or inert ingredient under 40 CFR 180.950(a) because it is considered a commonly 

consumed food commodity (USEPA 2010f;2022a).

USEPA (2022a) reviewed the Incident Data System and identified 15 reported incidents

associated with garlic oil, eight incidents pertaining to human health, six involving domestic 

animals, and one involving human health and a domestic animal. None of the incidents were 

serious, and all the products contained other active ingredients, such as capsaicin and egg solids.

USEPA waived data requirements for quantitative dietary (food and drinking water) exposure due 

to garlic oils' composition and physical and chemical properties, broad availability for human 

consumption, and its benefits to human health (USEPA 2022a).

6.2 Dose-Response Assessment

6.2.1 Human Health Dose-Response

Garlic oil has minimal human health hazards, is a commonly consumed food commodity, and has 

a significant history of exposure to humans, demonstrating minimal toxicity (USEPA 2022a).
30

USEPA has not yet assessed garlic oil under their Endocrine Disruptor Screening Program 

(USEPA 2022a). 

6.2.2 Ecological Effects Dose Response

USEPA waived all non-target organism and environmental fate data requirements for garlic oil

due to garlic oils’ natural occurrence, non-toxic mode of action as a repellent, and biodegradability

(USEPA 2022a). 

USEPA (2022a) reviewed the Incident Data System and identified four reported incidents 

associated with garlic oil. These incidents included minor exposure and damage to plants, 

although it is unclear if the damage resulted from garlic oil as the products also contained 

capsaicin and egg solids.

6.3 Exposure Assessment and Risk Characterization

6.3.1 Human Health Exposure and Risk Characterization

USEPA (2022a) concluded that applications of products containing garlic oil as the active 

ingredient according to label instructions would not result in harm to the general population or 

applicators.

6.3.2 Ecological Exposure and Risk Characterization

USEPA (2022a) concluded garlic oil would not result in a hazard or toxic risk to non-target 

organisms. The lack of toxicity and the environmental fate properties for garlic oil, WS use 

patterns, and the product label requirements indicate WS use of registered products containing 

garlic oil will not harm non-target terrestrial and aquatic species.

7 METHYL ANTHRANILATE

7.1 Problem Formulation

7.1.1 Chemical Description and Product Use

Methyl anthranilate (CAS number 134-20-3; synonyms: methyl-2-aminobenzoate and anthranilic 

acid, methyl ester) is a naturally occurring ester found in plants such as sunflowers, grapes, corn, 

cherries, cocoa, and black tea (USEPA 2011d;2020f). Methyl anthranilate is categorized as GRAS 

by FDA when used as a food additive (flavoring agent) (USEPA 2020f). 

Methyl anthranilate is a food and non-food use biopesticide or biochemical pesticide active 

ingredient when used as a non-toxic, non-lethal bird repellent (USEPA 2020f). Methyl anthranilate 

has been used as a bird repellent since the 1990s, though its bird repellency was first discovered 

in the late 1950s (Kare and Pick 1960). Several research studies found methyl anthranilate an 

effective bird repellent for turf, water, and fruit crops (Askham 1992, Avery 1992, Dolbeer et al. 

1992, Dolbeer et al. 1993, Mason et al. 1985). Methyl anthranilate acts by causing pain in birds 

by triggering the trigeminal nerve (USEPA 2020f). Birds exposed to methyl anthranilate associate 

the discomfort with the treatment area (USEPA 2018a). 

There are several registered end-use products with methyl anthranilate as the active ingredient, 

ranging from 14.5% to 40% w/w. Methyl anthranilate can be applied as a spray or a fog to repel 
31

pest birds for a range of food and non-food uses. The labels do not list mammals as target 

species. 

7.1.2 Physical and Chemical Properties

Methyl anthranilate (C8H9NO2) is a colorless to pale yellow liquid or crystal with bluish 

fluorescence and a grape-like odor with a slightly bitter or pungent taste (Burdock 2010). It has a 

melting point of 24–25oC and a boiling point of 256oC at 760 mm Hg (USEPA 2011g). It has a 

reported vapor pressure of 2.71 x 10-2 mm Hg at 25oC and a calculated air-water partition 

coefficient of 1.89 x 10-6 atm-m3

/mole at 25oC (NIH 2022b). Methyl anthranilate has a density of 

1.168 g/mL at 20oC (NIH 2022b). It is slightly soluble in water with a water solubility of 2,850 mg/L

at 25oC (NIH 2022b). It has a soil adsorption coefficient (Koc) of 75 (NIH 2022b).

7.1.3 Environmental Fate

Methyl anthranilate is non-toxic to humans and is classified as a biopesticide by EPA and GRAS

by FDA when used as a food additive. As a result, extensive environmental fate and groundwater 

data have not been submitted for the registration of methyl anthranilate. However, other publicly 

available environmental fate information is summarized below.

Methyl anthranilate degrades rapidly in the environment into non-toxic components such as 

anthranilic acid (USEPA 2020f). Methyl anthranilate is extremely volatile and will rapidly dissipate 

from foliar and soil surfaces, with an atmospheric half-life of 11 hours (NIH 2022b, USEPA 2011a).

Methyl anthranilate undergoes rapid photodegradation (USEPA 2020f). Methyl anthranilate is 

expected to have high mobility in soil based on an estimated Koc (NIH 2022b). However, mobility 

may be much slower in some soils as aromatic amines are expected to bind strongly to humus or 

organic matter (NIH 2022b). Volatilization from moist soil surfaces (based on its air–water partition 

coefficient) and soil biodegradation (100% biodegradation in 64 days) are expected to be 

important fate processes (NIH 2022b). In water, methyl anthranilate is not expected to adsorb to 

suspended solids and sediment based on the estimated Koc. Biodegradation in water may be an 

important environmental fate process as methyl anthranilate, present at 50 mg/L, exhibited 100% 

biodegradation in 20 days when incubated in dechlorinated, charcoal-filtered water (NIH 2022b).

Volatilization from water surfaces is rapid based on the estimated air-water partition coefficient

and estimated volatilization half-lives of 24 and 180 days for a model river and model lake, 

respectively (NIH 2022b). An estimated bioconcentration factor (BCF) of 8 suggests a low

potential for bioconcentration in aquatic organisms. Studies indicate hydrolysis is not expected to 

be an important environmental fate process (NIH 2022b).

7.1.4 Hazard Identification

Methyl anthranilate is a naturally occurring compound in plants such as sunflowers, corn, grapes, 

cherries, cocoa, and black tea (USEPA 2020f). It is often used as a flavoring in food and is 

considered GRAS by the FDA when used as a food additive (USEPA 2018a;2020f). USEPA 

evaluated exposure scenarios and found methyl anthranilate occurs at higher concentrations in 

commonly consumed foods, such as corn, grapes, cherries, cocoa, and black tea than in 

pesticidal exposure scenarios, indicating negligible risk to people (USEPA 2020f).
32

Methyl anthranilate is hydrolyzed in the small intestine to alcohol and either anthranilic acid or an 

N-alkyl anthranilic acid. In humans, anthranilic acid is a normal metabolite and is excreted in the 

urine primarily as o-amino hippuric acid and, to a lesser extent, as anthranilic acid glucuronide

(NIH 2022b). USEPA (2011d) found it unlikely that products containing methyl anthranilate will 

have adverse effects on human health.

USEPA found three reported incidents of methyl anthranilate exposure from January 1, 1992, to 

October 29, 2010. All incidents were attributable to misuse or to the inert ingredients in the product 

and not from the active ingredient, methyl anthranilate (USEPA 2011d). 

7.2 Dose-Response Assessment

7.2.1 Human Health Dose-Response

Acute Toxicity

Methyl anthranilate is virtually non-toxic to mammals through all routes of exposure. Methyl 

anthranilate is classified as Toxicity Category III for acute oral and dermal toxicity (Table 10). 

USEPA waived the inhalation toxicity study. Methyl anthranilate is an eye irritant but not a dermal 

irritant (Table 10) (USEPA 2011d). It is not a dermal sensitizer (USEPA 2011d). Limited data are 

available on the acute toxicity of anthranilic acid (a major metabolite of methyl anthranilate); 

however, an oral LD50 as high as 5,410 mg/kg-bw in rats has been reported, which indicates low

to no toxicity (NCBI 2022a). 

Table 10 Acute oral median lethality studies for mammals for Methyl anthranilate. 

Test Species Test

Result 

(Methyl Anthranilate 40-

98% w/w)

USEPA Toxicity 

Category

Laboratory Brown Rat (M) Acute Oral LD50 3,633 mg/kg-bw III

Laboratory Brown Rat (F) Acute Oral LD50 3,000 mg/kg-bw III

Laboratory Brown Rat Acute Oral LD50 3,288 mg/kg-bw III

Domestic Rabbit Acute Dermal LD50 >2,000 mg/kg-bw III

Laboratory Brown Rat Acute Inhalation LC50 Waived N/A 

Domestic Rabbit Primary Eye Irritation Slight to Moderate Irritant II

Domestic Rabbit Primary Dermal Irritation No Irritation IV 

Guinea Pig Dermal Sensitization Not a Sensitizer N/A 

M = male, F = female, N/A = Not applicable

Reference: (USEPA 2011d)

Subchronic and Chronic Toxicity

USEPA did not require information on subchronic and chronic toxicity because methyl anthranilate 

is a naturally occurring substance found in many foods, and it is unlikely products containing it 

will have adverse effects on human health (USEPA 2011d). 
33

Developmental and Reproductive Effects, Neurotoxicity Effects, Carcinogenicity and 

Mutagenicity, Immunotoxicity Effects, and Endocrine Effects

USEPA did not require information on developmental and reproductive effects, neurotoxicity 

effects, carcinogenicity, mutagenicity, immunotoxicity, or endocrine effects of methyl anthranilate

(USEPA 2011d). There is no known evidence that methyl anthranilate causes these types of 

effects or affects these systems in humans.

7.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Methyl anthranilate has moderate to slight acute toxicity to freshwater fish and is slightly toxic to 

aquatic invertebrates (i.e., water flea) (Table 11) (USEPA 2011a). Methyl anthranilate is 

practically non-toxic to freshwater fish on a dietary basis (USEPA 2011a). 

Table 11 Acute and chronic toxicity to aquatic vertebrates and invertebrates for methyl anthranilate.

Taxonomic 

group Test species Test Result (mg/L) Reference

Freshwater 

Fish

Atlantic Salmon (Salmo salar) LC50 34.28 (Clark et al. 1993)

Atlantic Salmon 96-hr LC50

32.25 

(slightly toxic) (USEPA 2011a)

Rainbow Trout 

(Oncorhynchus mykiss) LC50 23.47 (Clark et al. 1993)

Rainbow Trout 96-hr LC50

22.91–25.40 

(slightly toxic) (USEPA 2011a)

Channel Catfish (Ictalarus 

punctatus) LC50 20.08 (Clark et al. 1993)

Channel Catfish 96-hr LC50

16.23 

(slightly toxic) (USEPA 2011a)

Bluegill Sunfish (Lepomis 

macrochirus) LC50 19.80 (Clark et al. 1993)

Bluegill Sunfish 96-hr LC50

9.12–42.56 

(moderately to 

slightly toxic)

(USEPA 2011a)

Striped Bass (Morone 

saxatilis) 

12-hr dietary 

LC50 

(nonguideline)

>1,000 mg/kg 

(no effects on 

growth or 

survival)

(USEPA 2011a)

Freshwater 

Invertebrates

Water Flea (Daphnia magna) EC50 18.2 (Clark et al. 1994)

Aquatic freshwater 

invertebrates (not specified) 48-hr EC50

17–29.1

(slightly toxic) (USEPA 2011a)

Terrestrial Effects Analysis

The single dose oral LD50 for bobwhite quail was >2,036 mg/kg-bw, classifying methyl anthranilate 

as non-toxic to upland game birds (Table 12). The NOEL was 2,036 mg/kg-bw. In the mallard 

duck (Anas platyrhynchos), the dietary toxicity LC50 was >5,620 mg/kg-diet. This classifies methyl 

anthranilate as practically non-toxic to waterfowl. Methyl anthranilate is practically non-toxic to 
34

mammals (Table 12) (USEPA 2011a). Methyl anthranilate is practically non-toxic to the honey 

bee with a 48-hr contact toxicity LC50 >25 μg/bee (USEPA 2011a). 

Table 12 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds for methyl 

anthranilate. 

Test species Test Result Reference

Brown Rat (lab)

LD50 2,910 mg/kg-bw (Lewis 2004)

LD50 >5,000 mg/kg-bw (USEPA 2011a)

90-day dietary 

LC50

>500 mg/kg-bw/day

(no effects on growth or survival) (USEPA 2011a)

House Mouse (lab) LD50 3,900 mg/kg-bw (Lewis 2004)

Guinea Pig LD50 2,780 mg/kg-bw (Lewis 2004)

European Rabbit LD50 5,000 mg/kg-bw (Opdyke 1974)

Mallard Duck

LD50 >292 mg/kg-bw (USEPA 2011a)

LC50 >5,620 mg/kg-diet 

(practically non-toxic) (USEPA 2011a)

Bobwhite Quail LD50

>2,036 mg/kg-bw, 

>2,250 mg/kg-bw

(practically non-toxic)

(USEPA 2011a)

Ring-necked Pheasant Subacute LC50 >5,620 mg/kg-diet (USEPA 2011a)

White-crowned Sparrow LC50 >2,200 mg/kg-diet 

(practically non-toxic) (USEPA 2011a)

Methyl anthranilate applied at a rate of 18 kg/ha caused a minor foliar burn on 90% of sprayed 

blueberry leaves (Avery 1992). Additional studies showed the appearance of minor foliar 

desiccation or burn at greater than 2.0% methyl anthranilate concentration rates applied to 

raspberries and 8.0% concentrations applied to cherries, blueberries, and grapes (Askham 1992). 

However, the foliar desiccation in Askham (1992) was later attributed to the inert ingredients 

(surfactants) in the product and not to the methyl anthranilate (USEPA 2011a). 

7.3 Exposure Assessment and Risk Characterization

7.3.1 Human Health Exposure and Risk Characterization

WS mostly applies methyl anthranilate to repel birds at airports to prevent interference with 

aircraft. WS made one application on turf for Canada geese at an office park in Missouri and two 

agricultural applications to protect wheat fields in Oregon between FY11 and FY20. Applications 

are in areas where the general public is not present during the time of application. 

USEPA (2020f) evaluated residue levels at harvest when methyl anthranilate is used on food 

crops and concluded no significant residues were expected. Methyl anthranilate is not applied to 

potable water resources, and its environmental fate properties indicate movement into and 

persistence in water resources is unlikely. Low application rates and rapid biodegradation of 

methyl anthranilate result in a minimal risk of human exposure (USEPA 2018a). Therefore, the 

risk of injury to the general public is negligible.

Occupational exposure, particularly through inhalation and dermal contact, is possible for mixers 

and applicators; however, oral exposure through the ingestion of food and water contaminated 
35

with methyl anthranilate is not an expected exposure pathway. The labels for methyl anthranilate 

require applicators and handlers to wear long-sleeved shirts and long pants, waterproof gloves, 

and shoes plus socks (USEPA 2015b). The proper use of PPE will reduce dermal exposure.

Methyl anthranilate does not have mammalian toxicity, and residues in food and water are unlikely 

based on the use pattern and environmental fate (USEPA 2020f). USEPA (2011d) concluded 

methyl anthranilate would not cause harm to the general public based on its lack of toxicity. In 

addition, WS’s use pattern for methyl anthranilate does not expose the general public.

7.3.2 Ecological Exposure and Risk Characterization

The label restrictions for methyl anthranilate do not allow applications to potable water resources, 

reducing the exposure potential to aquatic species. Methyl anthranilate’s environmental fate 

properties, label restrictions, and WS use pattern indicate exposure to aquatic species is 

negligible. Based on the negligible aquatic exposure potential and its toxicity to aquatic species 

ranging from negligible to moderate (Table 11), there is negligible risk to aquatic species from the 

WS use of methyl anthranilate. 

Methyl anthranilate is non-toxic to practically non-toxic to mammals and birds (USEPA 2011a). 

WS expects target birds and any non-target birds exposed to experience discomfort from 

exposure, but the discomfort is of short duration, likely a minute or less after they leave the area 

with volatilized methyl anthranilate (Stevens and Clark 1998). Methyl anthranilate is not 

considered phytotoxic at the concentration in registered end-use products. Methyl anthranilate is 

practically non-toxic to terrestrial invertebrates, including pollinators. Methyl anthranilate is a 

naturally occurring substance found in many plant species to which invertebrates are exposed on 

a regular basis (USEPA 2011a).

WS does not anticipate risks to non-target organisms from using methyl anthranilate. WS use 

patterns and following product label instructions reduce exposure to non-target organisms. The 

USEPA determined methyl anthranilate will not negatively impact federally listed threatened or 

endangered species or designated critical habitats (USEPA 2011a).

8 NAPHTHALENE

8.1 Problem Formulation

8.1.1 Chemical Description and Product Use

Naphthalene (CAS number 91-20-3) is an organic compound derived from distilling coal tar and 

is classified as a benzenoid polycyclic aromatic hydrocarbon. Naphthalene’s pungent odor repels 

some animals, such as rabbits, squirrels, bats, dogs, and snakes. Naphthalene products are 

registered for non-food indoor and outdoor residential use. Indoor uses include placement in 

closed drawers, closets, and storage areas to control moths and in attics to repel squirrels and 

bats (e.g., mothballs). Outdoor uses are used around buildings and gardens to repel animals such 

as snakes and rabbits (USEPA 2008a).

Snake-A-Way® Snake Repelling Granules is a granular formulation that contains naphthalene 

(7%) and sulfur (28%; sulfur is covered in Section 11 of this risk assessment (Woodstream 
36

Corporation 2013). WS infrequently uses Snake-A-Way® Snake Repelling Granules (EPA 

Registration Number 58630-1) to repel certain snake species at outdoor use sites listed on the 

label (Table 2).

The Snake-A-Way® Snake Repelling Granules label identifies rattlesnakes (Crotalus spp.) and 

garter snakes (Thamnophis spp.) as target pest species to repel from residential dwellings, 

garages, barns, trailers, utility houses, woodpiles, trash cans, and flower beds. The label allows 

for use around the perimeter of flower gardens. The product may not be used at sites where

snakes are believed to be already present. The label does not allow for use in gardens or fields 

of crops grown for food or feed. The label does not allow applications near streams, ponds, pools, 

or water supplies or directly to water, including areas where surface water is present or intertidal 

areas below the mean high-water mark. 

Applications are made by hand in bands surrounding the area to be protected. Bands 4 to 5 inches 

in width are used for garter snakes, and bands 8 to 12 inches in width for rattlesnakes. The product 

is lightly sprinkled over the area within the treatment band. The label does not indicate an 

application rate. During the registration review, USEPA (2018b) determined that a high application 

rate for outdoor use of naphthalene products was 10.8 pounds a.i./acre based on information 

provided by the registrant (USEPA 2018b). Retreatment is recommended when the odor fades in 

seasons when the snakes are active.

8.1.2 Physical and Chemical Properties

Naphthalene (C10H8) is a white, crystalline solid with a characteristic coal-tar odor (USEPA 

2018d). Naphthalene has a vapor pressure of 0.085 mm Hg at 25oC, water solubility of 31.7 mg/L 

at 20oC, and a calculated air-water partition coefficient of 4.4 x 10-4 (NIH 2022a). Its log 

octanol/water partition coefficients (Kow) range from 3.29 to 3.37 (NIH 2022a, USEPA 2018d), 

which suggests a low potential for bioconcentration in aquatic organisms, and the log organic 

carbon coefficient (Koc) is 3.11 (ATSDR 2005).

8.1.3 Environmental Fate

Naphthalene is likely to volatilize from surface water based on its chemical properties. It has poor 

solubility in water (NIH 2022a). In water, naphthalene would largely remain in solution with small 

quantities binding to suspended solids and benthic sediments and degrades rapidly through 

photolysis and biological processes. In surface water, its photolysis half-life is about 71 hours 

(ATSDR 2005). Biodegradation is the dominant fate process for naphthalene in aquatic systems, 

with a half-life of about 7 days (ATSDR 2005). Naphthalene has moderate bioconcentration in 

aquatic organisms, but bioaccumulation in the food chain is not expected to occur (ATSDR 2005).

Naphthalene volatilizes from aerated soils (ATSDR 2005). Data from the open literature suggest 

that naphthalene binds relatively rapidly to soils, degrades with aerobic soil metabolism half-lives 

between 3.5 and 40 days, and has no apparent degradation under anaerobic soil conditions 

(USEPA 2018d). In aerobic soil, naphthalene biodegrades to carbon dioxide (ATSDR 2005). In 

sandy-loam soil with 0.5–1.0% organic carbon, naphthalene has a half-life of 203 days (ATSDR 

2005).
37

Naphthalene reacts with photochemically produced hydroxyl radicals and has an atmospheric 

half-life of less than one day (ATSDR 2005). The major products from this reaction are 1- and 2-

naphthol and 1- and 2-nitro naphthalene (ATSDR 2005). 

8.1.4 Hazard Identification

In humans and dogs, but not rodents, naphthalene causes red blood cell hemolysis after 

inhalation. Oral exposure and hemolysis are the most commonly reported toxicosis from 

naphthalene exposure (USEPA 2018d). Other symptoms of naphthalene-induced anemia include 

increased reticulocyte counts and serum bilirubin levels, Heinz body formation, fatigue, lack of 

appetite, restlessness, and pale appearance (ATSDR 2005, USEPA 2018d). In infants, hemolysis 

from naphthalene exposure can cause jaundice which can lead to permanent neurological 

damage, convulsions, motor disturbances, damage to mental faculties, and sometimes death 

(ATSDR 2005). Exposure of adults and children to large numbers of mothballs in their homes 

caused nausea, headache, malaise, and confusion (ATSDR 2005). 

In animal studies, naphthalene exposure has caused lens opacities (cataracts); however, the 

formation of cataracts in humans from naphthalene exposure is not verified (ATSDR 2005). In 

animal studies, naphthalene’s reactive metabolites produce neoplastic and nonneoplastic lesions 

in the respiratory tract (lung or nasal epithelial tissue) (ATSDR 2005). It causes glutathione 

depletion, lipid peroxidation, DNA fragmentation, and the production of active oxygen species 

(USEPA 2008b). 

The liver is expected to be the principal site of metabolism after oral exposure (ATSDR 2005). 

Metabolism in other tissues can also occur, including in the nasal olfactory epithelium, Clara cells 

in pulmonary epithelia, and eye tissue (ATSDR 2005). Excretion mostly occurs in urine (ATSDR 

2005). 

USEPA (2008c) summarized incident data for 1993 to 2005 from IDS, Poison Control Centers, 

California Department of Pesticide Regulation, and SENSOR and found most cases involved 

excessive, inappropriate, or misused indoor uses of naphthalene (e.g., mothballs) with accidental 

exposure to young children representing a high proportion of the cases. USEPA (2018d) updated 

their incident review and found incidents involving naphthalene had declined, but not ceased, 

since their previous review in 2008. The majority of incidents still involved inhalation exposures 

from homeowners’ indoor use of mothballs, and the most frequent symptoms reported were 

headache, diarrhea, nausea, and vomiting.

8.2 Dose-Response Assessment

8.2.1 Human Health Dose-Response

Acute Toxicity

Naphthalene is slightly toxic in acute oral and acute dermal routes of exposure (Toxicity Category 

III) (USEPA 2008a). The acute oral LD50 (rat) is 2,649 mg/kg-bw, and the acute dermal LD50 is 

>2,000 mg/kg-bw (USEPA 2008a). Naphthalene is moderately toxic (LC50 >0.4 mg/L) by the acute 

inhalation route (Toxicity Category II). It causes slight to moderate eye irritation and moderate 
38

skin irritation (Toxicity Category III). Naphthalene is not considered a skin sensitizer (USEPA 

2008a).

Subchronic and Chronic Toxicity

In a 90-day oral toxicity study in rats at 0, 25, 50, 100, 200, or 400 mg/kg-bw/day, the NOAEL for 

naphthalene was 100 mg/kg-bw/day, and the LOAEL was 200 mg/kg-bw/day (decreased body 

weights and renal effects) (USEPA 2018d). In the 400 mg/kg-bw/day group, both sexes displayed 

lethargy, hunched posture, and roughened coats. In a second 90-day oral toxicity study in mice 

at 0, 12.5, 35, 50, 100, or 200 mg/kg-bw/day, the NOAEL was 100 mg/kg-bw/day, and the LOAEL 

was 200 mg/kg-bw/day (rough hair and lethargy at weeks 3 and 4) (USEPA 2018y).

In a subchronic 30-day inhalation study (nose only) in rats at 0, 0.005, 0.016, 0.052, 0.157, or 

0.404 mg/L for 6 hours per day, the NOAEL was 0.016 mg/L, and the LOAEC was 0.052 mg/L 

(increased incidence and severity of nasal lesions) (USEPA 2018d). In a 90-day subchronic 

inhalation toxicity study (nose-only) in rats at 0, 0.010, 0.052, or 0.315 mg/L for 6 hours per day, 

the NOAEC was not identified. LOAEC was 0.010 mg/L based on increased incidence and 

severity of nasal lesions (USEPA 2018d).

In a subchronic 90-day dermal toxicity study in rats at 0, 100, 300, or 1,000 mg/kg-bw/day, the

only noted effects in the rat were at the high dose (limit test) of 1,000 mg/kg-bw/day (increased 

incidence and severity of excoriated skin and papules in both sexes, atrophy of seminiferous 

tubules in males, non-neoplastic lesions in the cervical lymph node, liver, thyroid, kidneys, urinary 

bladder and skin in females) (USEPA 2018d). The NOAEL was 300 mg/kg-bw/day. This study 

shows dermal toxicity is likely not a concern (USEPA 2008a).

Developmental and Reproductive Toxicity

There was no evidence of developmental toxicity (oral exposure) in rat and rabbit prenatal 

developmental toxicity studies or maternal effects in the rabbit study (USEPA 2008a;2018d). 

Doses were at 0, 50, 150, or 450 mg/kg-bw/day in the rat study and 0, 20, 80, or 120 mg/kgbw/day in the rabbit study. The maternal NOAELs were 50 mg/kg-bw/day in the rat study and 120 

mg/kg-bw/day in the rabbit study. The LOAEL was 150 mg/kg-bw/day (lethargy, slow breathing, 

rooting behavior, and decreases in body weight or increases in body weight and food and water 

consumption) in the rat study. Reproductive toxicity studies were not required by USEPA for 

registration as naphthalene as a non-food use pesticide (USEPA 2008a).

Neurotoxicity Effects

Neurotoxic effects were observed in the developmental toxicity (oral exposure) and an acute oral 

neurotoxicity study in rats but were only observed at higher bolus doses (USEPA 2018d). In the 

acute oral neurotoxicity study at 0, 400, 800, or 1,200 mg/kg-bw/day (oral exposure), the LOAEL 

was 400 mg/kg-bw-day (neurotoxicity symptoms were head shaking, reduced motor activity in 

males and females, and hunched posture in females) (USEPA 2018d). A neurotoxicity NOAEL 

was not identified.
39

In a subchronic neurotoxicity study (inhalation nose-only exposure) in rats at 0, 0.005, 0.052, or 

0.329 mg/L for 6 hours per day, the NOAEC was 0.005 mg/L, and the LOAEC was 0.052 mg/L 

based on nasal lesions (USEPA 2018d). 

Carcinogenicity and Mutagenicity

In two-year chronic inhalation studies with rats and mice exposed to naphthalene, carcinogenic 

effects were observed. In the rat study, nasal tumors of the olfactory epithelium and adenomas of 

the respiratory epithelium were observed. In the mouse study, there was a statistically significant 

increase in liver adenomas and adenomas and carcinomas combined. In female mice, there was 

an increase in alveolar/bronchiolar adenomas. The National Toxicology Program concluded from 

these studies that there is evidence of carcinogenic activity of naphthalene in male and female 

rats and some evidence of carcinogenic activity in female mice but not male mice (USEPA 2008a). 

Naphthalene is classified in Group C as a possible human carcinogen based on limited data on 

carcinogenicity in humans exposed to naphthalene via the oral and inhalation routes and limited 

evidence of carcinogenicity in animals via the inhalation route (USEPA 1998b). 

Immunotoxicity Effects

A 30-day oral exposure immunotoxicity study in female mice was conducted at 0, 25, 100, or 250 

mg/kg-bw/day (USEPA 2012b). The NOAEL was 100 mg/kg-bw/day, and the systemic toxicity 

LOAEL was 350 mg/kg-bw/day (reduced body weights and spleen and thymus weights). An 

immunotoxicity LOAEL was not established.

Endocrine Effects

Naphthalene is subject to the endocrine screening part of the Endocrine Disruptor Screening 

Program (USEPA 2018d). Listed substances will be assessed by computation and modeling 

methods for the potential of endocrine disruptive activity. Further quantification of endocrine 

activity will be evaluated for candidate substances in subsequent Tier 1 and Tier 2 studies.

8.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Naphthalene is moderately toxic to freshwater fish (96-hr LC50 of 2 mg/L and 3.2 mg/L for the 

rainbow trout (Oncorhynchus mykiss) and bluegill sunfish (Lepomis macrochirus), respectively) 

and aquatic invertebrates (48-hr LC50 of 1.6 mg/L for water flea) (Table 13) (USEPA 2008b). 

Chronic exposure of Coho salmon (Oncorhynchus kisutch) to naphthalene resulted in a 40-day 

LOAEC and NOAEC of 0.67 and 0.37 mg/L, respectively, with an observed reduction in feeding 

behavior, growth, and survival (USEPA 2008b). In an embryo-larvae toxicity study with the 

fathead minnow (Pimephales promelas), adverse effects were observed at 0.85 mg/L with a 

NOAEC of 0.62 mg/L (USEPA 2008b). Freshwater fish species act as surrogates for aquaticphase amphibians, indicating moderate toxicity for aquatic-phase amphibians (USEPA 2008b). 

It is slightly toxic to aquatic nonvascular plants, with a 48-hr EC50 of 33 mg/L for green algae 

(Chlorella vulgaris) (USEPA 2008b). Data was not available for aquatic vascular plants.
40

Table 13 Acute and chronic toxicity to aquatic vertebrates and invertebrates for naphthalene.

Taxonomic 

group Test species Test Result(mg/L) Reference

Freshwater 

Fish

Rainbow Trout (Oncorhynchus mykiss) 96-hr LC50

NOAEC

2.0

0.86

(USEPA 2008b)

(USEPA 2016a)

Bluegill Sunfish (Lepomis macrochirus) 96-hr LC50

NOAEC

3.2

1.4

(USEPA 2008b)

(USEPA 2016a)

Fathead Minnow (Pimephales promelas) 96-hr LC50 6.6 (USEPA 2008b)

(USEPA 2016a)

Aquatic 

Invertebrates

Water Flea (Daphnia magna) 48-hr EC50

NOAEC

1.6

0.48

(USEPA 2008b)

(USEPA 2016a)

Pacific Oyster (Crassostrea gigas) 96-hr EC50 199 (USEPA 2008b)

(USEPA 2016a)

Grass Shrimp (Palaemonetes pugio) 96-hr LC50 2.35 (USEPA 2008b)

(USEPA 2016a)

Terrestrial Effects Analysis

Naphthalene is classified as practically non-toxic to wild mammals due to a laboratory rat-acute 

oral LD50 of 2,649 mg/kg-bw (USEPA 2016a). Naphthalene is classified as practically non-toxic 

to upland game birds; the acute oral LD50 for bobwhite quail was 2,690 mg/kg-bw, and the NOAEC

was 810 mg/kg-bw (USEPA 2016a). The subacute dietary LC50 was >5,620 mg/kg-bw/day (Table 

14) (USEPA 2008b). Naphthalene toxicity to waterfowl species is unknown (USEPA 2008b). 

Toxicity data for honeybees is not available (USEPA 2008b;2016a). In studies on the chronic 

effects (reproduction and survival) of naphthalene on soil invertebrates, the springtail Folsomia 

candida had a NOAEC and LOAEC of 88 and 409 μmol/kg soil, respectively, and the annelid 

worm Enchytraeus crypticus had a NOAEC and LOAEC of 220 and 2045 μmol/kg soil, 

respectively (USEPA 2008b). 

No effects data is available for terrestrial plants (USEPA 2008b). 

Table 14 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds for 

naphthalene.

Test species Test Results Reference

Brown Rat (lab) Acute oral LD50 2,649 mg/kg-bw (USEPA 2008b)

(USEPA 2016a)

Bobwhite Quail

Acute oral LD50

NOAEC

2,690 mg/kg-bw

810 mg/kg-bw

(USEPA 2008a)

(USEPA 2016a)

Subacute dietary LC50 >5,620 mg/kg-bw/day (USEPA 2008a)

8.3 Exposure Assessment and Risk Characterization

8.3.1 Human Health Exposure and Risk Characterization

Naphthalene products are not registered for food uses or use on agricultural crops, and dietary 

exposure from food is not expected. USEPA determined outdoor post-application inhalation and 

dermal exposure to be negligible or minimal (USEPA 2018d). 
41

The acute dietary reference dose (RfD) for naphthalene is 0.4 mg/kg-bw/day based on an acute 

oral neurotoxicity study in rats where the LOAEL of 400 mg/kg-bw/day produced hunched posture 

in female rats, and head shaking and reduced motor activity in male and female rats (USEPA 

2008a;2018d). The acute RfD was derived using a 1,000-fold uncertainty factor (10x for interspecies extrapolation, 10x for intra-species variation, and 10x factor for LOAEL to NOAEL 

extrapolation) (USEPA 2018d). The chronic dietary RfD is 0.1 mg/kg-bw/day based on a study in 

rats with NOAEL of 100 mg/kg-bw/day and using a 1,000-fold uncertainty factor (10x for interspecies extrapolation, 10x for intra-species variation, and 10x factor for subchronic to chronic 

extrapolation) (USEPA 2018d). 

When used outdoors as an animal repellent, migration to water resources (drinking water) is 

potentially possible. USEPA (2008a;2018d) modeled dietary exposure and residential handler 

exposure (non-cancer) and risk estimates for naphthalene in drinking water. The risk estimates 

were all found to be below the acute and chronic RfD threshold levels of concern. Dietary 

exposures through drinking water and food are not expected for WS’s use of products containing 

naphthalene because of the label’s use restrictions and WS's low usage of the product.

The annual amount of naphthalene that WS uses in its animal damage management program is 

limited (Table 2). Between FY16 and FY20, WS only used an average of 0.2 pounds of products 

containing naphthalene and sulfur per year to repel rattlesnakes (Table 2). WS applicators adhere 

to label requirements, which include not applying the product to water or areas where surface 

water is present or intertidal areas below the mean high-water mark. Naphthalene is highly 

volatile, indicating the chemical’s concentration in water and on the ground would dissipate 

quickly. 

WS’s care in the selection of use sites minimizes any risks to the public, particularly small children, 

who may be at risk from accidental ingestion. Adherence to label requirements regarding PPE 

minimizes risk to WS workers who apply chemical repellents. Any exposure and risk would be 

short-term based on the methods for application and the low frequency of use for naphthalene by 

WS.

8.3.2 Ecological Exposure and Risk Characterization

Based on the application rates and naphthalene’s environmental fate properties, USEPA (2008b)

concluded that leaching into groundwater is not likely a significant route of exposure for non-target 

species to the pesticidal use of naphthalene.

USEPA (2008b) modeled aquatic exposures and found naphthalene applied at a rate of 10.8 

lb/acre six times, 60 days apart, posed a minimal acute risk to aquatic species (risks to aquatic 

vascular plants are unknown due to lack of toxicity data). This rate is greater than the labeled rate 

for the snake repellent.

Exposure routes for terrestrial species include direct episodic ingestion of naphthalene granules, 

ingestion of contaminated soil, and dermal contact with treatment surfaces (USEPA 2008b). 

Inhalation of naphthalene as it volatilizes from treated surfaces and airborne soil or pesticide dust 

particulates is also a possible exposure route (USEPA 2008b). USEPA (2018b) reviewed the 

Ecological Incident Information System for incidents through May 2018. Between 2008 and 2017, 
42

there were 3 separate incidents where 4 dogs died, and 1 dog had diarrhea after likely ingesting 

Snake-A-Way® Snake Repelling Granules applied in outdoor use sites. Based on these reported 

adverse incidents and the acute oral LD50s, USEPA (2018b) determined that birds and mammals 

that consume granules containing naphthalene could be at risk. 

Furthermore, birds may not be as repelled by naphthalene as other species. In a study on the 

effects of naphthalene on starlings, nest boxes were treated with up to 1.3 g of naphthalene per 

liter space, and no repellency was observed (Dolbeer et al. 1988). The authors noted that bird 

species differ in their olfactory sensitivities. Birds are a surrogate species for reptiles and 

terrestrial-phase amphibians; as with birds, the exposure will be much less as terrestrial-phase 

amphibians and reptiles do not reside strictly in the treatment area. In addition, naphthalene is 

used as a repellent for reptiles, and minimal consumption of granules is expected. 

Studies are lacking on naphthalene’s toxicity to terrestrial plants, and its potential risk to plants is 

unknown. 

Although the USEPA estimates above indicate adverse effects to some birds and mammals, 

USEPA indicates exposure would be much less because the estimate assumes that non-target 

species would only occur in the treatment area and exclusively feed on the naphthalene granules. 

WS has used naphthalene products minimally, with only one work task conducted in five years, 

with an average annual use of 0.2 pounds between FY16 and FY20 (Table 2). Label use 

requirements and the low application frequency indicate WS usage of naphthalene would have 

minimal impact on non-target species. However, should WS usage of naphthalene increase 

significantly, WS applications could possibly have some adverse impacts on non-target species.

9 OIL OF BLACK PEPPER/PIPERINE

9.1 Problem Formulation

9.1.1 Chemical Description and Product Use

Oil of black pepper (CAS number 8006-82-4; synonym and USEPA’s Chemical Name for the 

active ingredient: oils, black pepper) is a naturally occurring oil extract from the black pepper plant 

(Piper nigrum) derived via steam distillation of the plant’s dried, unopened fruit (USEPA 

2005b;2019b). 

Piperine (CAS number 94-62-2; synonym and USEPA’s Chemical Name for the active ingredient: 

Piperidine, 1-[(2E,4E)-5-(1,3-benzodioxol-5-yl)-1-oxo-2,4-pentadienyl]-) is responsible for the 

pungency of the naturally occurring black pepper plants’ dark brown to black berries or 

peppercorns (USEPA 2015c). Although piperine can be extracted from dried black peppercorns, 

it is manufactured synthetically for commercial uses (USEPA 2004b). 

Woodstream Corporation (Lititz, PA) applied to USEPA to register a pesticide product (Animal 

Repellent Granular, alternative brand name Havahart® Critter Ridder®; EPA Registration number 

50932-10) containing both oil of black pepper and piperine in 2003 (USEPA 2003a). USEPA 

(2005a) draft registration review schedule for biopesticides put oil of black pepper and piperine 

under the same case number (6004). For this risk assessment, all of the data for oil of black 

pepper also applies to piperine. 
43

Oil of black pepper is a pungent oil that repels animals through irritation upon touching or tasting

the product (USEPA 2005b). The end-use products used to repel animals have concentrations of 

oil of black pepper ranging from 0.48 to 3.84% w/w active ingredient. Piperine concentrations in 

end-use products range from 0.185 to 1.48% w/w active ingredient. Oil of black pepper and 

piperine are currently registered as active ingredients in 3 products (USEPA 2019b).

WS may use and distribute products containing oil of black pepper and piperine to cooperators to 

repel animals such as dogs, cats, raccoons, squirrels, skunks, and groundhogs.

9.1.2 Physical and Chemical Properties

Oil of black pepper is a pale yellow liquid with an irritating, sharp peppery odor (USEPA 2004c).

Oil of black pepper has a vapor pressure of 5.3 mm Hg at 20oC, is insoluble in water, and has a 

boiling point of 187.8oC (USEPA 2005b).

Piperine (C17H19NO3) is a pale yellow to yellow crystalline solid with a pungent odor and burning 

aftertaste (USEPA 2004b). Piperidine compound has a vapor pressure of 1.3 x 10-7 mm Hg, a 

water solubility of 0.04 mg/mL at 18oC, and a boiling point of 498–499oC at 760 mm Hg (NIH 

2023b).

9.1.3 Environmental Fate

The need for environmental fate and groundwater data were not triggered for oil of black pepper 

and piperine because of practically non-toxic results (USEPA 2005b). Risks to non-target species 

is minimal due to the use pattern, application methods, and lack of toxicity (USEPA 2005b).

9.1.4 Hazard Identification

Oil of black pepper and piperine are allowed food additives by FDA. No registered pesticide

products containing oil of black pepper and piperine are approved for food use. Therefore, the 

USEPA did not require a tolerance or an exemption from the requirement of a tolerance for 

residues of oil of black pepper or piperine found in or on food (USEPA 2019b).

USEPA (2019b) reviewed the Incident Data System and identified one reported incident 

associated with oil of black pepper and piperine. The incident involved minor human health 

effects, including burning eyes and sore throat, and may be attributable to other ingredients in the 

formulated product (i.e., capsaicin).

9.2 Dose-Response Assessment

9.2.1 Human Health Dose-Response

Oil of black pepper and piperine pose minimal human health hazards. Oil of black pepper and 

piperine are widely used as flavoring agents in foods and have a significant history of exposure 

to humans, demonstrating minimal toxicity (USEPA 2005b). A qualitative risk assessment for oil 

of black pepper and piperine was considered adequate by USEPA (USEPA 2005b) due to their

uses as flavoring agents and in aromatherapy. Due to the use pattern, demonstrated low toxicity,

and low concentration of oil of black pepper and piperine in registered products, USEPA (2005b)

determined dietary exposure risk is not of concern for the registered repellent products. There is 

also no significant risk of toxicity effects from oral, dermal, or eye irritation or inhalation exposure 
44

to oil of black pepper or piperine, and any potential pesticidal residues of oil of black pepper or 

piperine in food and drinking water are negligible (USEPA 2005b). 

Based on the available data, no endocrine system-related effects have been identified for oil of 

black pepper or piperine, and none are expected (USEPA 2005b). 

9.2.2 Ecological Effects Dose Response

Oil of black pepper and piperine are considered to have minimal to no toxicity to mammals, given 

their widespread use as food additives, or to birds. Mallard ducks (Anas platyrhynchos) received 

a single oral dose of the end-use product Animal Repellent Granular in capsules in an acute oral 

toxicity study, which resulted in no mortality and no effect on body weight or feed consumption 

over 14 days. The acute oral LD50 was >2,250 mg/kg-bw (USEPA 2005b). Based on the low avian 

acute oral toxicity, USEPA (2005b) granted a waiver for freshwater fish, invertebrates, and 

nontarget insect toxicity data requirements.

9.3 Exposure Assessment and Risk Characterization

9.3.1 Human Health Exposure and Risk Characterization

USEPA (2005b) concluded that applications of products containing oil of black pepper and 

piperine as the active ingredients according to label instructions would not result in harm to the 

general population or applicators.

9.3.2 Ecological Exposure and Risk Characterization

USEPA (2005b) concluded oil of black pepper and piperine would not result in a hazard or toxic 

risk to non-target organisms. The lack of toxicity and the environmental fate properties for oil of 

black pepper and piperine, WS use patterns, and the product label requirements indicate WS use 

of registered products containing oil of black pepper and piperine will not harm non-target 

terrestrial and aquatic species.

10 POLYBUTENE

10.1 Problem Formulation

10.1.1 Chemical Description and Product Use

Polybutene (CAS number 9003-29-6; synonym: polybutene oligomer) is a synthetic, nondrying 

liquid or gel. Polybutene is a homopolymer (same repeating unit) or oligomer of the monomer 

butene (CAS Number 106-98-9; C4H8), both normal and isobutene (USEPA 2010c). Polybutene 

is not toxic but repels birds and mammals because of its sticky nature. Polybutene is registered 

for outdoor terrestrial non-food and residential uses on buildings or adjacent structures (e.g., 

bridges, overpasses, beams, girders, ledges, windowsills, gutters, trees, shrubs, vines) and for 

indoor non-food use. Polybutene is used to prevent birds, such as pigeons and starlings, from 

perching or roosting and to prevent damage to trees by beavers (USEPA 2010c). 

Polybutene is the sole active ingredient in 4 the Birds® Bird Repellent (93% w/w USEPA

Registration Number 8254-5) and Hot Foot® Bird Repellent (93.5% w/w; USEPA Registration

Number 55943-1). These products are tactile repellents labeled to repel pigeons and starlings 

from roosting or perching. It is also the active ingredient in 4 the Birds® Transparent Bird Repellent 
45

Liquid (40% w/w; USEPA Registration Number 8254-3). This product is labeled to repel birds

(e.g., blackbirds, starlings) from roosting or perching on the inside supports of buildings and 

structures or branches of trees, bushes, and vines adjacent to buildings and structures. The 

product, 4 the Birds® Transparent Bird Repellent Liquid, may also be used to discourage beavers 

from damaging trees.

Products containing polybutene in a ready-to-use tube or caulking gun can be applied as a bead 

strip to surfaces. Liquid product may be applied evenly with a paintbrush or sprayed on with a 

hand or pressure sprayer (USEPA 1994). All labels emphasize the importance of a clean surface 

before applying the product. For repelling beaver damage to trees, the product is sprayed or 

brushed on the lower trunk areas (ground level up to two feet high). WS has not used products 

containing polybutene between FY11 to FY20 but may do so in the future.

10.1.2 Physical and Chemical Properties

Polybutene (C8H16) is an oily, odorless, colorless liquid. It is a viscous non-drying liquid at room 

temperature. The boiling point of polybutene is 160oC, and it decomposes at higher temperatures 

(USEPA 1994). Polybutene has a reported vapor pressure of 0.13 mm Hg at 25oC and an 

estimated– air-water partition coefficient of 4.88 x 105 atm-m3

/mol. Polybutene has a density of 

0.89 g/mL at 37.7oC. The water solubility of polybutene is <0.1%, negligible. It will float on water.

The estimated Koc for polybutene is 2.5 x 109 L/kg (USEPA 2010c).

10.1.3 Environmental Fate

Polybutene is considered to be persistent to abiotic hydrolysis, direct photolysis in water (over the 

short term), and microbial degradation. It is not sensitive to metals, metal ions, or sunlight. 

Polybutene will change color, and its viscosity will decrease at elevated temperatures and over 

extended periods in the presence of oxygen. This photooxidation may generate epoxides, 

aldehydes, and carboxylic acids of low molecular weight. Breakdown of the polymer from 

oxidation of the double bond may cause a decrease in viscosity. Polybutene can adsorb strongly 

to soil or other surfaces (USEPA 1994;2010c).

10.1.4 Hazard Identification

The pesticidal mode of action of polybutene is mechanical in nature, not chemical, relying on an 

adhesive/sticky surface which, upon contact, discourages animals from roosting, perching, 

walking, or gnawing on treated surfaces (USEPA 1995;2010c;2014).

Polybutene has relatively low acute toxicity but causes eye irritation (USEPA 1995). Dermal 

toxicity is not anticipated based on the lack of oral effects and the expectation of low absorption 

due to the relatively large size of polybutene molecules. Inhalation toxicity is of low concern due 

to the expectation of limited exposure via this route, lack of toxicity in oral studies, and lung effects 

in rats only following inhalation exposure at very high exposure concentrations (USEPA 2022g). 

No food-related uses are registered, so dietary exposure is not of concern.

10.2 Dose-Response Assessment

10.2.1 Human Health Dose-Response
46

Acute Toxicity

The acute oral LD50 in the rat is >5,000 mg/kg-bw (Toxicity Category IV), and the acute dermal 

LD50 is >2,000 mg/kg-bw in the rabbit (Toxicity Categories III) (USEPA 1994;2010c). Polybutene 

is not irritating to the skin (Toxicity Category IV) but is irritating to the eyes (Toxicity Category II)

(USEPA 1995). Polybutene is not a sensitizer. A primary eye irritation study with rabbits resulted 

in transient corneal opacity and iritis at 24 and 48 hours, with conjunctival irritation through day 

10, for washed eyes, or day 14, for unwashed eyes (USEPA 1994) (Table 15). 

Table 15 Acute oral median lethality studies for mammals for Polybutene. 

Test Species Test Result USEPA Toxicity Category

Rat Acute Oral LD50 >5,000 mg/kg-bw IV

Domestic Rabbit Acute Dermal LD50 >2,000 mg/kg-bw III

Domestic Rabbit Primary Eye Irritation Irritating II

Domestic Rabbit Primary Dermal Irritation No Irritation IV 

Guinea Pig Dermal Sensitization Not a Sensitizer N/A 

N/A = Not applicable. Reference: (USEPA 2010c)

Subchronic and Chronic Toxicity

In a non-guideline 90-day oral toxicity study (rat) the NOAEL was 2,500 mg/kg-bw/day (the only 

dose tested), and the LOAEL was not determined (>2,500 mg/kg-bw/day) (USEPA 2010d). There 

was no toxicity in males or females (body weight changes, hematological and limited clinical 

chemistry parameters, organ weights, and histopathology) at 2,500 mg/kg-bw/day. 

USEPA (USEPA 2022g) assessed the conclusions of the Final Report on the Safety Assessment 

of Polybutene by the Cosmetic Ingredient Review (CIR) Scientific Panel in their Final Report on 

the Safety Assessment of Polybutene (1982). In a two-year oral study (rat), no significant toxicity

or increased tumor incidence was observed at doses that tested up to 20,000 mg/kg-bw 

polybutene in the diet. Beagle dogs administered doses up to 1,000 mg/kg-bw/day for two years 

also showed no adverse effects.

In a two-week inhalation study, male Wistar rats were exposed to polybutene aerosol (7 hrs/day, 

5 days/week) at 0, 0.07, or 0.7 mg/L. At 0.7 mg/L, three mortalities occurred, and pulmonary 

edema and hyperemia were also observed (USEPA 2010d). These effects were attributed to 

polybutene's oily, viscous, and water-insoluble physical properties, which may coat or clog 

airways at high ambient concentrations rather than a systemic effect. No effects were observed

at the lowest dose (0.07 mg/L). Additional inhalation data were not required since effects were 

only observed at the highest concentration, and inhalation exposure to polybutene from current 

uses is expected to be minimal (USEPA 2022g). 
47

Developmental and Reproductive Toxicity, Neurotoxicity Effects, Carcinogenicity and 

Mutagenicity, Immunotoxicity Effects

No target organs were identified following oral exposure to polybutene. Several oral studies, 

including subchronic rat, chronic dog, rat reproduction, and developmental toxicity studies, were 

reviewed by the CIR Scientific Panel (1982) and found no toxic doses at or above the limit dose 

(USEPA 2022g). Oral dietary exposure to rats (30/sex/dose) of polybutene at 0, 200, 4,000, or 

20,000 mg/kg-bw showed no effects except for possible treatment-related mortality in males at 

the limit dose of 20,000 mg/kg-bw. No other findings were reported, and no toxicity was observed 

in females. The published study evaluating developmental toxicity of polybutene reported no 

reproductive or offspring toxicity in rats exposed to 20,000 mg/kg-bw in the diet (USEPA 2022g). 

There was no evidence of immunotoxicity, carcinogenicity, or mutagenicity for polybutene 

(USEPA 2022g). 

Endocrine Effects

USEPA exempted polybutene from the requirement for Endocrine Disruptor Screening due to 

polybutene being an insoluble organic polymer with a molecular weight >1,000 Daltons that is 

highly stable. Polybutene is not anticipated to produce in humans or any other organism an effect 

similar to that produced by a naturally occurring estrogen, androgen, or thyroid hormone (USEPA 

2014). 

10.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Due to the insolubility of polybutene, USEPA waived the requirements for freshwater fish and 

aquatic invertebrate toxicity studies (USEPA 2010c). 

Terrestrial Effects Analysis

Polybutene is practically non-toxic to mammals and birds from acute exposures (Table 16) 

(USEPA 2010c). Birds are surrogates for reptiles and terrestrial-phase amphibians; therefore, 

polybutene is likely practically non-toxic to reptiles and terrestrial-phase amphibians. Small birds 

contacting the sticky material may become entrapped, or their feathers coated with gel, making 

them unable to fly. An entrapped bird or bird coated with polybutene gel may result in fatality

(USEPA 2010c). 

Table 16 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds for 

polybutene.

Test species Test Result

Brown Rat (lab) Acute oral LD50 >5,000 mg/kg-bw/day

Bobwhite Quail Acute oral LD50 >2,150 mg/kg-bw/day

Subacute dietary LC50 >5,000 mg/kg-bw/day

Reference: (USEPA 2010c)

10.3 Exposure Assessment and Risk Characterization

10.3.1 Human Health Exposure and Risk Characterization
48

Exposure to polybutene through dietary exposure is unlikely. Polybutene products have no 

labeled agricultural uses or other uses that may expose food materials to polybutene residues. 

Polybutene is a sticky, water-insoluble substance that remains on the treated surface. Based on 

existing use patterns, contamination of surface or groundwater sources of drinking water from 

outdoor use is unlikely (USEPA 2022g). Polybutene products are not highly volatile. Dermal 

exposure may occur from the use of the gel or liquid products; inhalation exposure may also occur 

from spray application of the liquid product. Inhalation exposure is not of concern because the 

registered formulations are either gels or water-based liquids (USEPA 2010c). Inhalation 

exposure from the gel formulation is not of concern due to the use pattern and application method 

(paintbrush and caulking gun) (USEPA 2022g). WS does not anticipate exposure to the general 

public. The 4 the Birds® Bird Repellent label requires occupational workers to wear protective 

eyewear such as goggles or a face shield and to avoid contact with skin. As such, WS expects 

minimal dermal, inhalation, and eye exposure of workers to polybutene. 

USEPA (2022g) concluded that no risks to human health are expected from the use of 

polybutenes based on their low toxicity, environmental fate properties, and low exposure potential. 

WS has not used polybutene products recently; however, this does not indicate future use 

patterns. Should WS increase its use of polybutene, this assessment's exposure and risk 

conclusions would remain the same.

10.3.2 Ecological Exposure and Risk Characterization

Polybutene contamination of water bodies is not expected to occur due to the use sites and the 

sticky composition and insolubility of the end-use materials. Therefore, there is no undue risk to 

aquatic animals anticipated from the registered uses of polybutene (USEPA 1994). 

Applications of products containing polybutene may expose nontarget birds, mammals, reptiles, 

and the terrestrial stages of amphibians in the treatment area. Based on the nature of the test 

material, toxic exposure is not likely. However, small birds contacting the sticky material may be 

temporarily trapped, and their feathers coated with gel, rendering them unable to fly. USEPA 

(USEPA 1994) has some data indicating that such incidents occasionally occur. These incidents 

can be fatal for some small birds, but such incidents generally only involve one or several 

individuals (USEPA 1994). Because use sites are principally urban commercial and industrial 

buildings where small legally protected bird species are unlikely to be prevalent, the risk to most 

nontarget birds is alleviated (USEPA 1994). USEPA (2022g) reviewed the OPP IDS (2017-2022) 

and found 11 incidents involving polybutene resins classified as minor severity. USEPA (2022g)

also reviewed the CDC and Prevention/National Institute for Occupational Safety and Health 

Sentinel Event Notification System for Occupational Risk-Pesticides (SENSOR; 2010-2017) 

databases and did not find reported incidents involving polybutene. In 2009, the USEPA (2010c)

reviewed the Environmental Fate and Effects Division’s Environmental Incident Information 

System and found an incident involving 30–80 cedar waxwings. At least one waxwing was 

incapacitated, and at least one waxwing was killed from the use of a polybutene product in a 

building. Polybutene’s environmental fate properties, label requirements, the proposed WS use 

pattern, and the favorable toxicity data indicate negligible risk to non-target terrestrial and aquatic 

species with the exception of non-target migratory birds. WS adherence to the application of 

polybutene products according to label directions will minimize risk to non-target birds.
49

11 SULFUR

11.1 Problem Formulation

11.1.1 Chemical Description and Product Use

Sulfur (CAS number 7704-34-9; synonym: elemental sulfur) is naturally occurring in the 

environment (USEPA 1991). Sulfur is a pesticide active ingredient in several miticides, 

insecticides, fungicides, and fumigant rodenticides and is used as fertilizer (USEPA 1991;2013c). 

Sulfur is also a pesticide active ingredient in a rodent and snake repellent (granular formulation, 

28% w/w sulfur) used by WS with the product name Snake-A-Way® Snake Repelling Granules 

(USEPA Registration Number 58630-1), which also contains 7% w/w naphthalene (naphthalene 

is covered in Section 8). The odor of volatile sulfur compounds has been shown to repel 

herbivorous mammals like rodents (Nolte et al. 1994).

WS infrequently uses Snake-A-Way® Snake Repelling Granules (USEPA Registration Number

58630-1) to repel certain snake species at outdoor use sites listed on the label (Table 3). The 

Snake-A-Way® Snake Repelling Granules label identifies rattlesnakes (Genus Crotalus) and 

garter snakes (Genus Thamnophis) as target pest species to repel from residential dwellings, 

garages, barns, trailers, utility houses, woodpiles, trash cans, and flower beds. The label allows 

for use around the perimeter of flower gardens. The product may not be used at sites where 

snakes are believed to be already present. The label does not allow for use in gardens or fields 

of crops grown for food or feed; however, sulfur is exempt from the requirement for a tolerance 

(40 CFR 180.1246). The label does not allow applications near streams, ponds, pools, or water 

supplies or directly to water, including areas where surface water is present or intertidal areas 

below the mean high-water mark. 

Applications are made by hand in bands surrounding the area to be protected. Bands 4 to 5 inches 

in width are used for garter snakes, and bands 8 to 12 inches in width for rattlesnakes. The product 

is lightly sprinkled over the area within the treatment band. The label does not indicate an 

application rate. During the registration review for naphthalene, USEPA (USEPA 2018b)

determined that a high application rate for outdoor use of this repellent product was 10.8 lb 

a.i./acre based on information provided by the registrant (USEPA 2018b). Retreatment is 

recommended when the odor fades in seasons when the snakes are active.

11.1.2 Physical and Chemical Properties

There are many allotropes of sulfur, including rhombic or alpha S8, in the environment (USEPA 

2013b). Sulfur is an odorless, tasteless, yellow crystalline solid (USEPA 2013b). Sulfur has a 

melting point of 112.8–120oC, a boiling point of 444.6oC, a vapor pressure of 3.95 x 10-6 mm Hg 

at 30.4oC, and an air-water partition coefficient of 3.95 x 10-6 mm Hg at 30.4oC (USEPA 2013b). 

Sulfur is largely insoluble in water at 1.9 x 10-8 mol S8/L or 4.87 parts per billion (USEPA 2013b).

11.1.3 Environmental Fate

USEPA (2013c) waived the environmental fate data requirements for sulfur because sulfur is 

ubiquitous and naturally occurs in water and soil (USEPA 1991). When applied to the 

environment, sulfur rapidly enters the natural environmental sulfur cycle (Komarnisky et al. 2003, 

USEPA 2013b). In this cycle, sulfur oxidizes into sulfate (SO4

2-

, under aerobic [oxic or suboxic] 
50

conditions) and reduces into sulfide (S2-

, under anaerobic [anoxic] conditions), mainly mediated 

by microbes (USEPA 2013b). The subsequent fate of sulfide depends on metal sulfide 

precipitation or volatilization to hydrogen sulfide (H2S; gas) (USEPA 2013b). The dissipation of 

sulfate is dependent on leaching and soil organic matter immobilization (USEPA 2013b). 

11.1.4 Hazard Identification

Sulfur can cause skin and eye irritation (USEPA 2013c). The number and severity of human health 

adverse incidents are relatively low and are mainly due to the irritating properties of sulfur (USEPA 

2013c). Chronic (lifelong) exposure to sulfur dust, as occurs for mineworkers, showed ocular 

disturbances, chronic bronchitis, and respiratory and sinus effects (USEPA 1991).

11.2 Dose-Response Assessment

11.2.1 Human Health Dose-Response

Acute Toxicity

Sulfur has very low acute oral toxicity and is Toxicity Category IV with an acute oral LD50 >5,000 

mg/kg (USEPA 2013c). The acute dermal and inhalation toxicity for sulfur are Toxicity Category 

III (USEPA 2013c). The dermal LD50 is >2,000 mg/kg-bw in rats (USEPA 2013c). The acute 

inhalation toxicity is >2.56 mg/L for a 4-hour exposure (USEPA 2013c). Sulfur can cause skin 

(moderate erythema and slight edema) and eye irritation and is Toxicity Category III for both 

(USEPA 2013c). Sulfur is not a sensitizer (USEPA 2013c). 

Subchronic and Chronic Toxicity, Developmental Toxicity, Mutagenicity, Immunotoxicity

Chronic exposure to sulfur is the natural state for all living organisms since sulfur is ubiquitous in 

the environment, and most aquatic and terrestrial environments are high in sulfur (USEPA 1991). 

Therefore, USEPA has waived the subchronic and chronic oral exposure data requirements for 

sulfur during registration and registration review (USEPA 2013c). 

In one 28-day dermal toxicity study, the only finding was an increased incidence of hyperkeratosis 

in both sexes at 1,000 mg/kg-bw/day, the highest dose level tested (USEPA 2013c).

There are no known risks of oncogenic, teratogenic, or reproductive hazards associated with 

sulfur, and metabolites are well known to be intermediary or end products of mammalian 

metabolic reactions (USEPA 1991;2013c).

Sulfur is not carcinogenic, genotoxic in bacteria and mammalian cells, or mutagenic to 

microorganisms (USEPA 1991;2013c).

11.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Available toxicity data submitted to USEPA and from the open literature indicates that sulfur is 

practically nontoxic to freshwater fish, freshwater aquatic invertebrates, and aquatic-phase 

amphibians on an acute basis (Table 17) (USEPA 2013b). The 96-hour LC50 values for two fish 

species, bluegill sunfish (Lepomis macrochirus) and rainbow trout (Oncorhynchus mykiss), were 
51

greater than 180 mg/L (USEPA 2013b). The 48-hour LC50 for the water flea (Daphnia magna) 

was greater than 5,000 mg/L, and the 96-hour LC50 for mysid shrimp (Americamysis bahia) was 

greater than 736 mg/L (USEPA 2013b). 

Table 17 Acute and chronic toxicity to aquatic vertebrates and invertebrates for sulfur.

Taxonomic 

group Test species Test Result (mg/L)1 Reference

Freshwater 

Fish

Bluegill Sunfish (Lepomis macrochirus) 96-hr LC50 >180 (USEPA 2013b)

Rainbow Trout (Oncorhynchus mykiss) 96-hr LC50 >180 (USEPA 2013b)

Western Mosquitofish (Gambusia affinis) Acute LC50 >10,000 (USEPA 2013b)

Aquatic 

Invertebrates

Water Flea (Daphnia magna) 48-hr LC50 >5,000 (USEPA 2013b)

Mayfly (Cloeon dipterum) Acute LC50 >40 (USEPA 2013b)

Mysid Shrimp (Americamysis bahia) 96-hr LC50 736 (USEPA 2013b)

Eastern Oyster (Crassostrea virginica) 96-hr EC50 736 (USEPA 2013b)

Amphibians Bog Frog (Rana limnocharis) LC50 2,560 (USEPA 2013b) 1 Concentrations greatly exceeded sulfur’s solubility in water. The sulfur was primarily in suspension (particulate sulfur; some 

precipitates were documented) or was lost via volatilization as hydrogen sulfide (H2S) (USEPA 2013b). 

Terrestrial Effects Analysis

Sulfur is practically nontoxic to mammals and birds and, by extension, to reptiles and terrestrialphase amphibians (USEPA 2013b). Sulfur had an oral LD50 of greater than 5,000 mg/kg-bw for 

rats (USEPA 2013b). In an 8-day dietary study in bobwhite quail (Colinus virginianus), the LC50

was >5,620 mg/kg-diet (USEPA 2013b). 

Sulfur is practically nontoxic to honey bees on an acute oral and contact basis (USEPA 2013b). 

Toxicity data are not available for terrestrial plants and were waived during registration and 

registration review (USEPA 2013b). 

11.3 Exposure Assessment and Risk Characterization

11.3.1 Human Health Exposure and Risk Characterization

The annual amount of sulfur that WS uses in its animal damage management program is limited 

(Table 3). Between FY16 and FY20, WS only used an average of 0.2 pounds of the product 

containing the active ingredients sulfur and naphthalene per year to repel rattlesnakes (Table 3). 

WS applicators adhere to label requirements, which include not applying the product to water or 

areas where surface water is present or intertidal areas below the mean high-water mark.

The currently-registered repellent product containing sulfur and naphthalene is not registered for 

food uses or use on agricultural crops, and dietary exposure from food is not expected. When 

used outdoors as an animal repellent, the migration of sulfur to water resources (drinking water) 

is not expected due to sulfur being practically insoluble and rapidly entering the environmental 

sulfur cycle, the label’s use restrictions, and WS's low usage of the product.

The sulfur in the repellent product could potentially irritate airway passages and eyes if applicators 

were accidentally exposed. WS’s care in the selection of use sites minimizes any risks to the 

public, particularly small children, who may be at risk from accidental exposure. Adherence to 

label requirements regarding PPE minimizes risk to WS workers who apply chemical repellents. 
52

Any exposure and risk would be short-term based on the methods for application and the low 

frequency of use as a chemical repellent by WS.

11.3.2 Ecological Exposure and Risk Characterization

Once released, sulfur is rapidly incorporated into the environmental sulfur cycle (USEPA 2013b). 

Sulfur is practically insoluble in water. Therefore, minimal exposure is expected to aquatic species 

from any runoff (USEPA 2013b). Even if exposure occurs, sulfur is practically non-toxic to aquatic 

species (USEPA 2013b). 

Some terrestrial plant species may be adversely affected by registered sulfur applications. As of 

2013, there were only 5 ecological incident reports involving terrestrial plants in the Ecological 

Incident Information System (EIIS) for sulfur (USEPA 2013b). However, all 5 occurred between 

1999 and 2001, and USEPA rated only one as “probable” (USEPA 2013b). 

Ingestion by non-target terrestrial vertebrate and invertebrate species visiting the outdoor use 

sites is possible following applications of repellent products containing sulfur, but sulfur likely does 

not pose a toxicological concern to non-target species (USEPA 2013b). No ecological incidents 

are reported for any other terrestrial species despite sulfur’s extensive use in various pesticide 

products (USEPA 2013b). However, USEPA (2018b) did review the EIIS for naphthalene 

incidents through May 2018. Between 2008 and 2017, there were 3 separate incidents where 4 

dogs died, and 1 dog had diarrhea after likely ingesting Snake-A-Way® Snake Repelling Granules, 

which contains both naphthalene and sulfur, applied in outdoor use sites. Based on these reported

adverse incidents and the acute oral LD50 values for naphthalene and sulfur, these deaths were 

attributed to naphthalene rather than sulfur exposure (USEPA 2018b). 

Label use requirements and the low application frequency indicate WS usage of sulfur as a 

repellent would have minimal to no impact on non-target species. Even if WS’s usage of sulfur 

increase significantly, WS applications of sulfur are unlikely to have adverse impacts on nontarget species.

12 THIRAM

12.1 Problem Formulation

12.1.1 Chemical Description and Product Use

Thiram (CAS number 137-26-8; synonyms: tetramethylthiuram disulfide and 

tetramethylthioperoxydicarbonic diamide) is a dimethyl dithiocarbonate compound primarily used 

as a food-use and non-food use fungicide with broad-spectrum antimicrobial properties (USEPA 

2020e). Thiram products are commonly used as a foliar spray on strawberries and peaches to 

control fungal pests and as a seed treatment to protect against fungal damage to seeds of a 

variety of food crop groups (Liu et al. 2022, USEPA 2021b). Thiram products are also registered 

as fungicidal foliar treatments for commercial coniferous, evergreen, and softwood trees, dip 

treatments for ornamental bulbs and roots, and seed treatments for flowering and non-flowering 

ornamental seeds (USEPA 2021b). In higher concentrations, thiram is also registered as a taste 

repellent applied directly to vegetation to repel rabbits, rodents, and deer. A tolerance or tolerance 

exemption is not required for these uses. Taste repellents deter rodents and rabbits from 
53

damaging trunks of trees/saplings and deter deer and elk from inhabiting airport property by 

rendering forage plants unpalatable. 

In 2021, USEPA proposed canceling all non-seed treatment and repellent uses of thiram in their 

proposed interim registration review decision due to unreasonable human and ecological risks 

outweighing the benefits (USEPA 2021b). Their final interim decision had not yet been finalized 

as of March 2023.

In the future, WS may utilize registered thiram concentrate products, such as DeerPro® Winter 

Animal Repellent (25.8% thiram; USEPA Registration Number 84178-1) or Defiant Turf Fungicide 

and Animal Repellent (75% thiram; USEPA Registration Number 45728-21), at non-food use 

sites, including airport runways, trees, vines, and shrubs, to prevent rabbit, deer, and rodent 

depredation. However, USEPA (USEPA 2021b) proposed the future cancellation of soluble 

concentrate and liquid formulations, including DeerPro® Winter Animal Repellent, but this product 

had not yet been canceled as of March 2023. In 2021, USEPA indicated that water-dispersible 

granular repellent formulations like Defiant Turf Fungicide and Animal Repellent could remain 

registered, but with some additional label revisions, such as limiting the allowed application 

methods for repellents containing thiram to spray applications that use a manually pressurized 

hand wand (USEPA 2021b). 

12.1.2 Physical and Chemical Properties

Thiram (C6H12N2S4) is a dimethyl dithiocarbamate, solid and crystalline at room temperature, with 

a melting point of 142–150oC. Thiram has a density of 0.32–0.35 g/mL, octanol/water partition 

coefficient of 39.5–54.2, a vapor pressure of 1.6–1.8 x 10 –5 mm Hg at 25oC and is slightly soluble 

in water (0.00165 g/100 mL) (USEPA 2021b). 

12.1.3 Environmental Fate

Thiram is of low to moderate persistence in soil and water. It is only slightly soluble in water (30 

mg/L) and has a strong tendency to adsorb to soil particles, and thus is not expected to 

contaminate groundwater. Thiram has a soil half-life of 15 days and degrades more readily in 

acidic soils and soils high in organic matter. Thiram has been shown to persist for up to 2 months 

in sandy soil but disappeared within one week from compost soil (USEPA 2020g). The major 

metabolites of thiram in soil are copper dimethyl dithiocarbamate, dithiocarbamate, 

dimethylamine, and carbon disulfide. In soil, thiram can be degraded by microbial action or 

hydrolysis under acidic conditions. Thiram is rapidly broken down in water by hydrolysis and 

photodegradation, especially under acidic conditions (Lazo and Miller 2014). Thiram’s mobility 

class is slightly mobile to hardly mobile (Koc = 2,245 to 24,526 mL/goc in 4 soils). Therefore, 

leaching to groundwater should be minimal. However, thiram has the potential to reach surface 

water through runoff via erosion or spray drift (USEPA 2020g).

12.1.4 Hazard Identification

Thiram is rapidly absorbed, distributed, extensively metabolized, and excreted primarily via 

expired air and urine in laboratory rats with no major differences between sexes (USEPA 2020e). 

In a metabolism and pharmacokinetics study in rats, expired air, urine, and feces account for 47–

48%, 33–35%, and 3–5% of the administered dose exposures. Urine analysis 24 hours postexposure detected no parent compound and five by-products of thiram metabolism. Expired air 
54

contained radio-labeled carbon dioxide, carbamyl sulfide, and carbon disulfide. Bioaccumulation 

of thiram is low (2–4%) after a single dose, and 2–3% is recovered from tissues at 4 days postdosing after repeated doses (USEPA 2020e). 

Repeated oral exposure to thiram causes toxicity in the liver (bile duct hyperplasia) in dogs and 

rats, toxicity to blood (anemia) in mice and rats, and toxicity to the eyes and urinary tract in mice 

(USEPA 2020e). There are no carcinogenicity or mutagenic/genotoxic risks from thiram 

exposures (USEPA 2020e). Subchronic inhalation exposures to thiram can cause neurotoxic 

effects, adverse effects on the thymus, olfactory epithelial degeneration in the nasal passage, and 

hyperplasia of the larynx (USEPA 2020e). Subchronic dermal exposures may also cause toxicity

to the liver (USEPA 2020e).

From January 1, 2010, to December 30, 2014, no human adverse effects incidents were reported 

in the main OPP Incident Data System (IDS) (USEPA 2015d). However, there were 28 minor 

incidents reported in the aggregate IDS during that period. USEPA (2015d) also reported that the 

SENSOR-Pesticides injury database documented 14 cases that involved thiram between 1998–

2011 and 9 cases involving only thiram, with 8 of the 9 cases being work-related. USEPA also 

summarized that eight cases were low in severity, and one was moderate in severity, with dermal 

symptoms reported in five cases and respiratory irritation reported in four cases.

According to the USEPA (2015d), from 2010 to 2014, 1 incident was reported to National Pesticide 

Information Center (NPIC) involving thiram. The USEPA summarized the incident involved a 45-

year-old male that sold vegetable seeds. He was handling seeds treated with a fungicide 

containing thiram and did not wear PPE. He developed a rash on both his hands and feet. This 

incident was classified with a certainty index of possible and a severity of moderate (USEPA 

2015d).

USEPA (2021b) updated this review, and from January 1, 2015, to February 5, 2020, there was 

1 incident in IDS involving just thiram and 14 incidents reported to Aggregate IDS with low severity

(USEPA 2020e;2021b). In SENSOR-Pesticides, there were 6 cases of low severity involving 

thiram between 2012 and 2015 (USEPA 2021b).

12.2 Dose-Response Assessment

12.2.1 Human Health Dose-Response

Acute Toxicity 

Thiram falls into Category III for acute oral toxicity, with an LD50 of 3,713 mg/kg-bw in male rats, 

1,778 mg/kg-bw in female rats, and 2,638 mg/kg-bw combined (USEPA 2020e). Thiram has an 

acute dermal LD50 of >2,000 mg/kg-bw (Category III) and an acute inhalation LC50 of >2.06 mg/L 

(Category IV) (USEPA 2020e). Thiram causes eye irritation (reversible redness, chemosis, and 

iritis; Category II-III) and is slightly irritating to the skin (Category IV) (USEPA 2020e). Thiram is a 

moderate skin sensitizer (USEPA 2020e).
55

Subchronic and Chronic Toxicity 

In a 90-day oral toxicity study in rats, the NOAEL could not be verified (no stability data for the 

test substance), and the LOAEL was 25 mg/kg-bw/day, based on decreases in body weights, 

hematology, and adverse changes to clinical chemistry (USEPA 2020e). In a 90-day oral toxicity 

study in dogs, the NOAEL was 1.9 mg/kg-bw/day, and the LOAEL was 6.3 mg/kg-bw/day, based 

on adverse changes to clinical chemistry, and decreases in body weights and food consumption 

(USEPA 2020e).

In a combined dietary chronic toxicity/carcinogenicity study, the NOAELs for rats (male/female or 

M/F) were 1.5/1.8 mg/kg-bw/day and the LOAELs were 7.3/8.9 mg/kg-bw/day, based on changes 

in hematology, adverse changes to clinical chemistry, and bile duct hyperplasia (USEPA 2020e).

In a 21-day dermal toxicity study in rabbits, the systemic NOAEL was 300 mg/kg-bw/day, and the 

LOAEL was 1,000 mg/kg-bw/day, based on decreases in body weights and food consumption, 

and adverse changes in clinical chemistry (USEPA 2020e). The dermal NOAEL was not 

determined, and the LOAEL was 100 mg/kg-bw/day, based on microscopic dermal lesions.

In a 28-day inhalation study in rats, the systemic NOAEC was 0.012 mg/L/day and the LOAEC 

was 0.025 mg/L/day, based on decreased locomotor activities in males, decreased thymus 

weights and histopathologic changes in the thymus in females (USEPA 2020e). The inhalation 

NOAEC and LOAEC were the same, based upon degeneration of olfactory epithelium and 

hyperplasia in the larynx in both sexes (USEPA 2020g).

Developmental and Reproductive Toxicity 

In a prenatal developmental study in rats, the maternal NOAEL was 15 mg/kg-bw/day, and the 

LOAEL was 30 mg/kg-bw/day, based on decreased body weights and placental weights (USEPA 

2020e). The developmental NOAEL was 15 mg/kg-bw/day, and the LOAEL was 30 mg/kgbw/day, based on decreased fetal body weights. In a prenatal developmental study in rabbits, the 

maternal and developmental NOAELs were 10 mg/kg-bw/day, and the LOAELs were not 

determined (USEPA 2020e).

In a two-generation reproduction and fertility effects study in rats, the parental NOAEL was 5 

mg/kg-bw/day, and the LOAEL was 14 mg/kg-bw/day, based on decreased body weights during 

gestation and lactation in F0 and F1 generations and pre-mating in F1 males and females (USEPA 

2020e). The offspring NOAEL was 2 mg/kg-bw/day, and LOAEL was 5 mg/kg-bw/day for rats, 

based on decreased body weights in the F1 and F2 generation offspring. The reproductive NOAEL 

was >12.2 mg/kg-bw/day, and the LOAEL was not determined.

In a developmental neurotoxicity study in rats, the maternal NOAEL was 3.7 mg/kg-bw/day, and 

the LOAEL was 7.2 mg/kg-bw, based on decreased body weight, food consumption, palpebral, 

tremors, cold to touch, and drooping eyes (USEPA 2020e). The offspring NOAEL was 1.4 mg/kgbw/day, and the LOAEL was 3.7 mg/kg-bw/day based on increased locomotor activity in females 

on post-natal day 17. 
56

Neurotoxicity Effects 

Thiram appears to cause neurotoxic effects at high dose levels. In an oral acute neurotoxicity 

screening battery study in rats, the NOAEL for neurotoxicity was 5 mg/kg-bw, and the LOAEL was 

150 mg/kg-bw, based on reduced motor activity at 3.5 hours and 7 and 14 days post-dosing 

(USEPA 2020e). USEPA (2020e) conducted a benchmark dose (BMD) analysis, and the 

benchmark dose level of one standard deviation (BMDL1SD) from 56 mg/kg-bw was 24 mg/kgbw (USEPA 2020g).

As described in the previous section, a developmental neurotoxicity study in rats found increased 

locomotor activity in female offspring on post-natal day 17 at the LOAEL of 3.7 mg/kg-bw/day 

(NOAEL = 1.4 mg/kg-bw/day) (USEPA 2020e).

Carcinogenicity and Mutagenicity 

The EPA classifies thiram as “not likely to be carcinogenic to humans” based on studies showing 

no evidence of carcinogenicity in rat and mouse carcinogenicity studies (dietary exposure) 

(USEPA 2020e). The NOAELs for mice (M/F) were 2.5/3.1 mg/kg-bw/day, and the LOAELs were 

24/57 mg/kg-bw/day, based on changes in mean body weights (gains and losses), anemia, and 

non-neoplastic lesions in the eyes, non-glandular stomach, and urinary bladder. The NOAELs for 

rats (M/F) were 1.5/1.8 mg/kg-bw/day, and the LOAELs were 7.3/8.9 mg/kg-bw/day, based on 

changes in hematology, clinical chemistry, and bile duct hyperplasia.

Additionally, thiram is not considered to be mutagenic/genotoxic as it did not induce DNA repair 

in rat hepatocytes or cause a significant increase in the frequency of micronucleated 

polychromatic erythrocytes (USEPA 2015d). The EPA has also not commissioned a Cancer 

Assessment Review Committee report for thiram. The EPA Hazard Identification Assessment 

Review Committee, in a 1999 report, identified thiram as a clastogenic agent due to experimental 

observations of cell growth progression disturbances at 2.4 μg/mL. The EPA states that “thiram 

was shown to act as a clastogen probably during the S-phase (one of the most tightly regulated 

cell transition points), strongly suggesting that cells will not progress to the next phase of the cell 

cycle and will, therefore, not proliferate” (USEPA 2020e).

Immunotoxicity Effects 

In an immunotoxicity study in mice, the systemic NOAEL was 74 mg/kg-bw/day, and the LOAEL 

was not determined (USEPA 2020e). The immunotoxicity NOAEL was 25 mg/kg-bw/day, and the 

LOAEL was 74 mg/kg-bw/day, based on decreases in anti-sheep red blood cells (SRBC) antibody 

responses (USEPA 2020e).

Endocrine Effects 

Like many mammals, including human females, rodents undergo spontaneous ovulation 

mediated by norepinephrine hypothalamic control of the pituitary gland. Thiram, like other 

dithiocarbonates, is known to inhibit dopamine-β-hydroxylase (DBH) activity and decrease 

hypothalamic norepinephrine synthesis by blocking its conversation from dopamine. An 

interruption of dopamine conversion reduces gonadotropin-releasing hormone and the 

subsequent neuronal activation of luteinizing hormone (LH). It has been observed in rodent 
57

models that when a luteinizing hormone surge is blocked by thiram exposure as low as 12 mg/kgbw administered during the proestrus period of the estrus cycle, then ovulation will be delayed by 

24 hours. A reduction in litter size was observed when rats were permitted to mate under these 

conditions. Rats exposed to thiram during the critical proestrus period exhibited decreased 

numbers of fertilized oocytes, a 10-fold increase in the number of supernumerary sperm in the 

perivitelline space (Farmer and Stoker 2018, Stoker et al. 2003), and polyspermic zygotes (Austin 

and Braden 1953). USEPA has not yet assessed thiram under their Endocrine Disruptor 

Screening Program (USEPA 2020e).

12.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

Thiram is very highly toxic to freshwater and estuarine/marine invertebrates (Table 17) (USEPA 

2020g). The freshwater water flea (Daphnia magna) was observed to have a significant (p<0.05) 

19% reduction in dry weight at a chronic thiram exposure level of 0.040 mg/L and signs of toxicity, 

including lethargy, pale coloration, and diminutive size from thiram a.i. levels of 0.040 and 0.081 

mg/L. Mortality was 100% at the highest treatment level (0.081 mg/L) (USEPA 2020g). Thiram 

was very highly toxic to Pacific oyster (Crassostrea gigas) larvae based on increased abnormal 

development (USEPA 2020h). The 48-hr EC50 was approximately 0.0047 mg/L (there were 

uncertainties in the actual exposure concentrations). Thiram was very highly toxic to mysid shrimp

(Americamysis bahia), with a 96-hr LC50 of approximately 0.00336 mg/L (there were uncertainties 

in the actual exposure concentrations) (USEPA 2020a).

Thiram is high to very highly toxic to freshwater and marine/estuarine fish on an acute and chronic 

basis (USEPA 2020g). The most sensitive fish species for thiram is the Harlequin fish (Rasbora 

heteromorpha), with an LC50 of 0.007 mg/L for a typical end-use product containing 80% thiram 

(USEPA 2020g). The most sensitive warm-water fish is the bluegill sunfish (Lepomis 

macrochirus), with an observed LC50 of 0.042 mg/L, and the most sensitive cold-water fish is the 

rainbow trout (Oncorhynchus mykiss), with an observed LC50 of 0.046 mg/L (USEPA 2020g).

In a chronic thiram exposure life-cycle study, the freshwater fathead minnow (Pimephales 

promelas) had significant (p<0.05) reductions in spawning frequency (69.5%), egg production 

(76.0%), and 4-week survival (24%) at the LOAEC (0.0022 mg/L, NOAEC was 0.0011 mg/L) also, 

time to hatch was delayed by up to 2 days. USEPA determined this critical effect to be the most 

sensitive freshwater fish chronic endpoint (USEPA 2020g). 

For estuarine/marine fish, thiram is observed to be highly toxic to sheepshead minnow 

(Cyprinodon variegatus) with an observed acute LC50 of 0.540 mg/L. The sheepshead minnow 

exposed to thiram for a 28-day early life-stage study had significant (p<0.05) 4.6% and 12% 

reductions, relative to controls, in length and dry weight from exposure to 0.0020 mg/L (NOAEC 

was 0.00093 mg/L) (USEPA 2020g). 

Thiram is phytotoxic to aquatic plants. For the vascular aquatic plant duckweed (Lemna gibba), 

the IC50 was 1.6 mg/L, but the NOAEC was <0.0574 mg/L based on decreased frond numbers 

(USEPA 2020g). For a typical end-use product (71% thiram, the 96-hr NOAEC was 0.0010 mg/L,

and the IC50 was 0.0013 mg/L for the most sensitive endpoint (area under the curve) for the marine 
58

algae (diatom) Skeletonema costatum (USEPA 2020b). For the non-vascular freshwater algae 

(diatom) Navicula pelliculosa for a typical end-use product containing 71% thiram, the 96-hr 

NOAEC was 0.00026 mg/L, and the LC50 was 0.00058 mg/L for the most sensitive endpoint (yield) 

(USEPA 2020c). 

Table 18 Acute and chronic toxicity to aquatic vertebrates and invertebrates for thiram.

Taxonomic 

group Test species Test Result (mg/L) Reference

Freshwater Fish

Bluegill Sunfish

(Lepomis macrochirus) 96-hr LC50 0.042 (McCann 1968)(USEPA 2020g)

Rainbow Trout

(Oncorhynchus mykiss) 96-hr LC50 0.046 (USEPA 2020g)

Fathead Minnow

(Pimephales promelas) 

210-day 

NOAEC

LOAEC

0.0011

0.0022 (USEPA 2020g)

Marine/Estuarine 

Fish

Sheepshead Minnow

(Cyprinodon variegatus) 96-hr LC50 0.540 (Croudace et al. 1992, USEPA 2020g)

Sheepshead Minnow 34-day NOAEC

LOAEC

0.00093

0.0020 (USEPA 2020g)

Aquatic 

Invertebrates

Water Flea (Daphnia 

magna) 48-hr EC50 0.210 (Husson 1986)

Water Flea 21-day NOAEC

LOAEC

0.020

0.040 (USEPA 2020g)

Mysid Shrimp

(Americamysis bahia) 96-hr LC50

~0.00336

(95% C.I. 

0.0023–

0.0040)

(Thompson et al. 1992b)

(USEPA 2020a)

Pacific Oyster

(Crassostrea gigas) 48-hr EC50

~0.0047

(95% C.I. 

0.0042–

0.0053)

(Thompson et al. 1992a)

(USEPA 2020h)

95% C.I. = 95% confidence interval

Terrestrial Effects Analysis

Thiram is practically non-toxic to adult honey bees on an acute oral and contact and chronic oral 

basis. Thiram has an acute oral LD50 of >106 μg/bee, and contact LD50 of 73.7 μg/bee in honey 

bees, and a chronic oral 10-day NOAEL and LOAEL of >4.32 μg/bee/day (Atkins and Anderson 

1967, USEPA 2020g). However, thiram was observed to be highly toxic to honey bee larvae on 

an acute dietary basis, with an observed larval acute oral LD50 of 0.28 μg/larvae and NOAEL of 

0.090 μg/larvae (USEPA 2020g). Thiram is also highly toxic to honey bee larvae on a repeated 

dose dietary basis (22-day test), with a NOAEL of 0.0254 μg/larvae/day, LOAEL of 0.0757 

μg/larvae/day, and an ED50 of 0.0872 μg/larva/day (USEPA 2020d;g). 

Thiram is slightly to moderately toxic to birds on an acute basis, with the ring-neck pheasant as

the most sensitive bird species tested (Table 18) (USEPA 2020g). The most sensitive avian 

chronic endpoint was in mallard ducks (USEPA 2020g). A NOAEC and LOAEC of 9.6 and 39.7 

mg/kg-diet were determined based on significant reductions in egg sets (35%), viable embryos 

(46%), live 3-week embryos (46%), normal hatchlings (56%), 14-day survivors (56%), eggs 
59

set/eggs laid (11%), normal hatchlings/live 3-week embryos (22%), and normal hatchlings/eggs 

laid (26%) (Gallagher et al. 2001, USEPA 2020g). 

Thiram is categorized as slightly toxic to mammals based on a combined acute oral LD50 of 2,638

mg/kg-bw in rats (USEPA 2020e). Studies conducted in wild mammals (mink and ferret) resulted 

in a dietary LOAEL of 45 and 8 mg/kg, respectively (NOAEL could not be determined), with a 

critical effect of a decrease in hematocrit (Hornshaw et al. 1983). A large set of acute, chronic,

subchronic, and two-generation reproduction and fertility effects dietary studies with laboratory 

rodents and dogs are available for thiram and are described above in Section 12.2.1. 

Thiram does not appear to be toxic to most terrestrial plants up to at least 4.1 lb/acre (USEPA 

2020g). 

Table 19 Acute oral median lethality and subacute dietary toxicity studies for mammals and birds for thiram.

Test species Test Result Reference

Brown Rat (lab) Acute oral LD50

3,713 mg/kg-bw males

1,778 mg/kg-bw females

2,638 mg/kg-bw combined

(USEPA 2020e)

Domestic dog

90-day oral 

NOAEL

LOAEL

1.9 mg/kg-bw/day

6.3 mg/kg-bw/day (USEPA 2020e)

Mallard Duck LD50 >2,800 mg/kg-bw (Hudson et al. 1984)

Red-winged Blackbird Acute oral LD50 >100 mg/kg-bw (Schafer 1972, 

USEPA 2020g)

Ring-necked Pheasant Acute oral LD50 673 mg/kg-bw (Hudson et al. 1984, 

USEPA 2020g)

Bobwhite Quail Subacute LC50 3,950 mg/kg-diet (USEPA 2020g)

Canary (Serinus 

canaria) 8-day LC50 >4,240 mg/kg-diet (USEPA 2020g)

Mallard Duck 23-week NOAEC

LOAEC

9.6 mg/kg-diet/day

39.7 mg/kg-diet/day (reductions 

in egg sets, viable embryos, and 

survival of embryos, and 

hatchlings)

(USEPA 2020g)

12.3 Exposure Assessment and Risk Characterization

12.3.1 Human Health Exposure and Risk Characterization

Non-repellent and non-seed treatment uses of thiram include direct application to growing plant 

material, which may result in contamination of food and drinking water sources. Residential use 

is restricted, so non-occupation environmental exposures are often associated with adult and child 

contact with treated commercial areas, such as turf residues resulting from spray drift.

The highest risk of injury due to the use of thiram as an animal repellent is from acute occupational 

dermal and inhalation exposures. Handlers may be exposed to thiram by mixing and handling the 

pesticide prior to application, during pesticide application, and during post-application activities 

such as reentry to treated areas. 
60

The USEPA has established a chronic reference dose (RfD) for thiram of 0.015 mg/kg-bw/day 

(the NOAEL was 1.5 mg/kg-bw/day), which was derived from the results of two studies: 1) the 

thiram combined chronic/carcinogenicity study in a rat model with hematological changes, clinical 

chemistry changes, and increased incidences of bile duct hyperplasia observed at the lowestobserved adverse-effect level (LOAEL) of 7.3 mg/kg-bw/day) (USEPA 2020e). The USEPA has 

determined that the revised dermal-absorption factor for thiram is 15% (USEPA 2021b). When 

applied to the developmental neurotoxicity study NOAEL of 1.4 mg/kg-bw/day (USEPA 2020e), a 

dermal equivalent dose of 9.3 mg/kg-bw/day can be determined.

In their proposed interim registration review decision, USEPA (2021b) determined that nonrepellent and non-seed treatment uses did not pose an unreasonable health risk, but there are 

“unreasonable risks from dermal and inhalation exposures for thiram, even when assuming the 

use of PPE and engineering controls beyond what is on current product labels” for all other labeled

uses. USEPA further states, "Health risks from the use of thiram and its associated end-use 

products have shown to be unreasonable for non-seed treatment uses, except animal repellency

[emphasis added], when used according to current label directions and when additional mitigation 

measures are considered.” (USEPA 2021b). However, USEPA (2022d) later revised its

occupational risk assessment and determined that dermal occupational exposures were above 

the level of concern for repellent uses. Inhalation occupational exposures were also above the 

level of concern for repellent uses unless respirators were included in PPE. 

12.3.2 Ecological Exposure and Risk Characterization

Thiram is highly toxic to aquatic species, including fish, aquatic invertebrates, oysters, and shrimp. 

Label restrictions prohibit the use of thiram directly to water, areas where surface water is present, 

and intertidal areas below the mean high-water mark. Drift and runoff may be hazardous to aquatic 

organisms in adjoining areas (USEPA 2020e). To further mitigate these exposures, USEPA 

proposed adding additional environmental hazard statements for aquatic species and surface 

water advisory statements to the thiram product labels in the proposed interim decision for the 

registration review of thiram (USEPA 2021b).

The ring-neck pheasant and mallard duck are the most sensitive bird species for acute and 

chronic exposures (USEPA 2020g). USEPA (2021b) determined that birds were at risk from 

thiram products through contact and ingestion exposures and has proposed adding additional 

environmental hazard label statements to minimize or prevent these exposures.

Only the highest labeled foliar uses exceed the acute level of concern for non-human mammals. 

However, all chronic exposures exceed the level of concern for all foliar uses for small to mediumsized mammalian species. Acute and chronic levels of concern are exceeded for all thiram uses 

for birds, reptiles, and amphibians. USEPA (2021b) determined that mammals were at risk from 

thiram products through contact and ingestion exposures and has proposed adding additional 

environmental hazard label statements to minimize or prevent these exposures.

Based on available data, USEPA determined that there are potential acute and chronic risks to 

adult and larval honey bees from thiram use (USEPA 2021b). However, in 2021, USEPA 

proposed to add the following risk mitigation language to the label for Defiant Turf Fungicide and 
61

Animal Repellent, “Do not apply during bloom” (USEPA 2021b). Once the product label is 

amended, this or similar label language will minimize honey bee exposure to thiram when this 

product is used as a repellent for deer, rabbits, and rodents.

WS’s intent to utilize thiram as an animal repellent as per the label will result in higher 

concentrations applied to target foliage, as opposed to commercial fungicidal uses for thiram. 

When applying thiram to use sites where non-target animals may be present, care must be taken. 

There is a possible route of unintended exposure to sensitive aquatic or terrestrial species during 

the application of thiram post-application due to dislodgeable residues and runoff. Strict 

adherence to current and future product label mandates concerning application rates and 

methods will minimize the ecological impact of WS’s thiram use.

13 URINES, COYOTE, AND FOX

13.1 Problem Formulation

13.1.1 Chemical Description and Product Use

Urines from coyotes and foxes (CAS numbers not assigned) are the active ingredients within 

repellent products registered to repel various pest mammals (deer, elk, domestic cats, 

groundhogs, armadillo, beavers, javelina, rabbits, woodchucks, opossums, pocket gophers, 

porcupines, shrews, voles, and moles) at residential indoor and outdoor non-food use sites, 

including lawns, flower beds, the perimeter of food-producing garden beds, garages, sheds, attics, 

and basements (USEPA 2019a). Predator urine products applied as repellents can deter other 

animals from feeding or denning in particular areas because the odor causes the target herbivore 

pests to avoid the area (USEPA 2016b). 

Urines from predators such as coyotes and big cats have been reported effective in preventing 

deer damage and damage from other vertebrate animals (Sullivan et al. 1985, USEPA 2009d).

Urine concentrated from animals that eat meat volatilizes and emits an odor that rodents will 

avoid, regardless of the predator species (Nolte et al. 1994). Browsing or feeding by deer and 

rodents was reduced when food items were treated with whole urines (100%) from predators that 

consumed higher content meat diets versus urines from animals that consumed vegetables 

(Lewison et al. 1993, Nolte et al. 1994). The specific substance(s) in the urine that triggers 

behavioral avoidance in target mammals is unknown (USEPA 2016b), but studies suggest that 

predator urines have higher amounts of sulfur-containing volatiles (Lewison et al. 1993, Nolte et 

al. 1994). Non-pesticidal uses of predator urines include use as lures and use by game hunters 

to mask their human scent. However, urine products sold for these non-pesticidal uses cannot be 

distributed or used as animal repellents (pesticides) without first being registered.

Coyote and fox urines are ubiquitous in nature, readily biodegradable, and thus, are regulated by 

USEPA as biopesticides or biochemical active ingredients (USEPA 2018e;2019a). Coyote and 

fox urines are similar in composition and in their registered uses, and therefore, their risk profile 

is considered to be the same (USEPA 2019a).

Currently-registered products contain either coyote urine at 5% w/w, fox urine at 5% w/w, or are 

a combination product that contains both urines (3.5% w/w coyote urine, 1.5% w/w fox urine) 
62

formulated into “ready-to-use” granules or in capsules. Granules and capsules are placed or 

sprinkled by hand on the ground, or hangable packs can be hung 1–4 feet above the ground to 

create an olfactory barrier or fence around the area to be protected. A granule product containing 

both urines may also be sprinkled directly into rodent burrows. In the future, WS may use repellent 

products containing coyote and/or fox urines to deter various mammalian pests from bedding, 

denning, burrowing, or feeding at labeled use sites. Urine products do not hold up well in inclement 

weather conditions, so they must be reapplied as necessary.

13.1.2 Physical and Chemical Properties

Coyote and fox urines are naturally-occurring mixtures of water (approximately 95% w/w), urea 

(approximately 3.6% w/w; CAS number 57-13-6), and the remaining ~1.4% consists of creatinine, 

sodium, calcium, phosphate, chloride, potassium, and magnesium (USEPA 2016b;2018e). 

Unprocessed coyote and fox urines are yellow liquids with an ammonia-like scent (USEPA 

2004a). They are stable when stored in sealed containers at ambient temperatures and have a 

vapor pressure of 23.756 mm Hg at 25°C (USEPA 2004a).

13.1.3 Environmental Fate

Coyote and fox urines break down rapidly in the environment and are considered to have no to

low persistence (USEPA 2018e). 

13.1.4 Hazard Identification

As of May 2019, there were no adverse human incidents reported for coyote or fox urines in 

USEPA’s Incident Data System (USEPA 2019a). 

Manufacturers of repellent products containing coyote and fox urines must process the urines to 

eliminate any zoonotic pathogens below the threshold of concern (USEPA 2019a).

None of the coyote or fox urine components are known endocrine disruptors or related to any 

known endocrine disruptors (USEPA 2004a).

13.2 Dose-Response Assessment

13.2.1 Human Health Dose-Response

Acute Toxicity

Coyote and fox urines have low toxicity (USEPA 2016b). USEPA waived the human health effects 

toxicity data requirements for coyote and fox urines during registration and registration review 

(USEPA 2019a). There is toxicity data available for urea, the primary non-water constituent in 

coyote and fox urines, at approximately 3.6% w/w (USEPA 2016b). Urea is non-toxic to mammals 

based on acute oral toxicity (LD50 was >5,000 mg/kg-bw, Toxicity Category IV; (USEPA 2016b). 

Urea is a slight dermal irritant (Toxicity Category IV) and is not considered to be a skin sensitizer 

(USEPA 2016b).

Subchronic and Chronic Toxicity, Developmental Toxicity, Mutagenicity, Immunotoxicity

USEPA waived the human health effects data requirements for subchronic, chronic, and

developmental toxicity, mutagenicity, and immunotoxicity for coyote and fox urines due to their 
63

significant history of exposure to humans (they are ubiquitous in the environment), and based on 

the existing toxicity data for urea (USEPA 2016b). Urea and the other constituents within coyote 

and fox urines are not structurally related to any known mutagen or belong to any chemical class 

of compounds containing known mutagens (USEPA 2016b). 

13.2.2 Ecological Effects Dose-Response

Aquatic Effects Analysis

USEPA waived the ecotoxicity data requirements for fish, aquatic invertebrates, and aquatic 

plants for coyote and fox urines during registration and registration review (USEPA 2016b). Urea, 

the primary non-water constituent in coyote and fox urines, is practically non-toxic to freshwater 

invertebrates and fish (Table 20; (USEPA 2016b). 

Table 20 Acute and chronic toxicity to aquatic vertebrates and invertebrates for urea.

Taxonomic group Test species Test Result 

(mg/L) Reference

Freshwater Fish Barna Baril (Barilius barna) 96-hr LC50 >9,100 (USEPA 2016b)

Ide (Leuciscus idus melanotous) 48-hr LC50 >10,000 (USEPA 2016b)

Aquatic Invertebrates Water Flea (Daphnia magna) 24-hr EC50 >10,000 (Husson 1986, 

USEPA 2016b)

Terrestrial Effects Analysis

USEPA waived the ecotoxicity data requirements for avian, mammal, terrestrial invertebrate, and 

terrestrial plant toxicity for coyote and fox urines during registration and registration review 

(USEPA 2016b). Urea is considered to be non-toxic to practically nontoxic to birds, mammals, 

and insects (Table 21; (USEPA 2016b). The acute oral and dietary lowest lethal dose for urea 

was 16,000 mg/kg-bw in pigeons, which is eight times higher than the maximum dose level 

typically used in an ecotoxicity pesticide registration study (USEPA 2016b). 

Coyote and fox urines are not considered phytotoxic at the low concentrations (≤5% w/w) 

contained within the registered products (USEPA 2018e). 

Table 21 Toxicity studies for mammals, birds, and terrestrial invertebrates for urea.

Test species Test Result Reference

Brown Rat (lab) Acute oral LD50 >5,000 mg/kg-bw (USEPA 2016b)

Pigeon Acute oral lowest lethal dose 16,000 mg/kg-bw (USEPA 2016b)

Acute dietary lowest lethal dose 16,000 mg/kg-bw (USEPA 2016b)

Yellow Fever Mosquito 

(Aedes aegypti larva) 4-hr LC50 60,000 mg/L (USEPA 2016b)

13.3 Exposure Assessment and Risk Characterization

13.3.1 Human Health Exposure and Risk Characterization

Coyote and fox urines used to produce registered repellent products come from domesticated 

coyotes and foxes raised on ranches (USEPA 2004a). The manufacturers of coyote and fox 
64

urines are required by USEPA to demonstrate that they have eliminated any zoonotic pathogens 

below the threshold of concern (USEPA 2019a). 

Coyote and fox urine repellent products are not registered for food use (USEPA 2016b). The 

product labels do not allow applications to aquatic areas, and coyote and fox urines are readily 

biodegradable in the environment (USEPA 2016b). Therefore, dietary exposures through food 

and drinking water are negligible (USEPA 2016b). 

The urea within coyote and fox urines can cause slight skin irritation, but urea comprises only 

about 3.6% w/w of coyote and fox urines, which in turn are ≤5% w/w of the registered products 

(USEPA 2016b). Therefore, registered coyote and fox urine repellent products are not expected 

to be a dermal irritant (USEPA 2016b). 

Any future use by WS of repellent products containing coyote and fox urines would have negligible 

risk to the general public or WS applicators based on their environmental fate properties, label 

language, and low toxicity profile.

13.3.2 Ecological Exposure and Risk Characterization

As of May 2019, no adverse ecological incidents were reported in the Ecological Incident 

Information System for coyote or fox urines (USEPA 2019a). 

The labels for repellent products containing coyote and fox urines do not allow applications to 

aquatic areas, which reduces aquatic exposure risk (USEPA 2016b). The rapid breakdown of 

coyote and fox urines in the environment indicates runoff or leaching into water resources would 

be negligible.

The low-use volumes, use sites, biodegradability, and lack of phytotoxicity or persistence in the 

environment indicate repellents containing coyote and fox urines pose little to no exposure risk to 

terrestrial species. Furthermore, predator urines are already ubiquitous in the environment 

(USEPA 2016b). Target pest animals visiting the residential use sites allowed on the labels for 

these products will be repelled and will avoid further exposure. Dietary exposure to terrestrial 

species is also not expected (USEPA 2016b). 

The USEPA determined that there will be no effects on federally listed threatened and 

endangered species or designated critical habitats from registered uses of repellent products 

containing coyote and fox urines (USEPA 2016b). 

14 UNCERTAINTIES AND CUMULATIVE IMPACTS

The uncertainties associated with this risk assessment arise primarily from a lack of information 

about the effects of chemical repellents, their formulations, metabolites, and potential mixtures on

non-target organisms that can occur in the environment. These uncertainties are not unique to 

this assessment but are consistent with uncertainties in human health and ecological risk 

assessments with any environmental stressor. 

Another uncertainty in this risk assessment is the potential for cumulative impacts on human 

health and the environment from the proposed use of chemical repellents. The potential for 
65

cumulative impacts is expected to be minimal based on the low volume and minor use of chemical 

repellents in the various WS uses. Areas where cumulative impacts may occur include: 1) 

repeated worker and environmental exposures to chemical repellents from program activities and 

other sources, 2) exposure to other chemicals with a similar mode of action, and 3) exposure to 

other chemicals affecting the toxicity of chemical repellents.

There is higher uncertainty on the potential cumulative impacts for any future use of thiram by WS

compared to the other registered chemical repellent active ingredients. USEPA has determined 

that although thiram has a low oral and dermal acute lethality (Toxicity Category III), thiram has a 

high acute lethality through the inhalation route and is an ocular irritant. USEPA (2021b) proposed

the cancellation of all non-seed treatment thiram uses, except animal repellency, due to 

“significant risks to occupational handlers” and ecological risks to the environment. Depending on 

WS use, there is a risk of occupational and non-occupation exposure in humans. To minimize 

occupational hazards of thiram exposure, the USEPA proposes the termination of non-seed 

treatment uses, except for animal repellency use, prohibition of product formulation types for 

specific crops for seed treatment uses, and the doubling of layers of PPE with a respirator for 

some seed treatment scenarios (USEPA 2020e). 

Repeated exposures that could lead to significant risk from chemical repellents are not expected 

due to label requirements that prevent significant exposure. Accidental exposure may occur from 

improper use of PPE, but the potential for this is unlikely because WS applicators follow label 

requirements regarding PPE and are trained in the use of PPE. 

Cumulative impacts are not expected from the use of chemical repellents. This is an area of 

uncertainty since it is unknown what other stressors, including chemicals, humans, and non-target 

wildlife, may be exposed to during a chemical-repellent application. 

From a human health perspective, cumulative impacts on human health are expected to be 

negligible because of these chemical repellents' mostly favorable toxicity profiles and label 

requirements minimize exposure risks to workers and the public (Table 22). The lack of exposure 

and risk to the public suggests that cumulative impacts would also be incrementally negligible 

when factoring in other stressors. 

Cumulative impacts on ecological resources are also expected to be incrementally negligible.

When utilized according to label mandates, risks of the reviewed chemical repellents to aquatic 

resources and most terrestrial non-target wildlife are low due to relatively low toxicity and 

mitigated exposure pathways (Table 23). 

Table 22. Summary of chemical repellent toxicity to humans.

Active ingredient

Exposure Route FDA 

Classification

for Food 

Additives

Dermal1 Ocular1 Inhalation1 Oral1

Ammonium soaps 

of fatty acids Non-toxic Moderate toxicity Non-toxic Non-toxic N/A

Anthraquinone Low toxicity Low toxicity Non-toxic Non-toxic N/A

Capsaicin Non-toxic Non-toxic Low toxicity Non-toxic GRAS
66

Egg solids Non-toxic Low toxicity Non-toxic Non-toxic GRAS

Garlic oil Non-toxic Non-toxic Non-toxic Non-toxic GRAS

Methyl anthranilate Low toxicity Moderate 

toxicity Waived Low toxicity GRAS

Naphthalene Low toxicity Low toxicity Moderate 

toxicity Low toxicity N/A

Oil of black pepper

Piperine Non-toxic Non-toxic Non-toxic Non-toxic GRAS

Polybutene Low toxicity Moderate 

toxicity Waived Non-toxic N/A

Sulfur Low toxicity Low toxicity Low toxicity Non-toxic N/A

Thiram Low toxicity Moderate 

toxicity High toxicity Low toxicity N/A

Urines, Coyote and 

Fox Non-toxic Non-toxic Non-toxic Non-toxic N/A

1 Non-toxic/Very low toxicity (Toxicity Category IV), low toxicity (Toxicity Category III), moderate toxicity (Toxicity Category II), high 

toxicity (Toxicity Category I)
67

Table 23. Summary of chemical repellent acute toxicity to aquatic and terrestrial species.

Active 

Ingredient

Aquatic species Terrestrial species Freshwater Estuarine/Marine

Fish Invertebrate Fish Invertebrate Amphibian Plant Invertebrate Bird Mammal 

(wildlife)

Reptile/ 

Amphibian Plant

Ammonium 

soaps of fatty 

acids

Slightly 

toxic Slightly toxic Nontoxic Slightly toxic Slightly 

toxic -- Practically 

non-toxic

Practically 

non-toxic

Practically 

non-toxic

Practically 

non-toxic 2

Phytotoxicity 

can occur

Anthraquinone Low toxicity Slight to high 

toxicity

Low 

toxicity High toxicity Low toxicity

1

Low 

toxicity Low toxicity Low toxicity Practically non-toxic

Low toxicity

2 --

Capsaicin -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3

Egg solids -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3

Garlic Oil -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3

Methyl 

anthranilate

Slight to 

moderate 

acute 

toxicity; 

practically 

non-toxic

on a dietary 

basis

Slight toxicity -- --

Slight to 

moderate 

acute 

toxicity 1

-- Practically 

non-toxic

Practically 

non-toxic

Practically 

non-toxic

Practically 

non-toxic 2

May cause 

foliar burn

Naphthalene Moderately 

toxic

Moderately 

toxic -- -- Moderately toxic 1

Slightly 

toxic -- Practically non-toxic

Practically 

non-toxic

Practically 

non-toxic 2 --

Oil of black 

pepper

Piperine

-- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 Practically 

non-toxic -- 3 -- 3 -- 3

Polybutene -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 Practically 

non-toxic

Practically 

non-toxic

Practically 

non-toxic 2 --

Sulfur Practically 

non-toxic

Practically 

non-toxic -- -- Practically non-toxic -- 3 Practically non-toxic

Practically 

non-toxic

Practically 

non-toxic

Practically 

non-toxic 2 -- 3

Thiram Very highly 

toxic

Very highly 

toxic

Highly 

toxic

Very highly 

toxic

Slightly 

toxic 2 

Nontoxic

Practically 

non-toxic to 

highly toxic 4 

Slightly 

toxic

Moderately 

toxic

Slightly toxic

2 Non-toxic

Urines, coyote 

and fox -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3

1 Data was unavailable for aquatic-phase amphibians. Fish are a surrogate species. 2 Data was unavailable for terrestrial-phase amphibians and reptiles. Birds are surrogate species. 3 This chemical is non-toxic. USEPA waived toxicity data requirements. 4 Thiram is practically non-toxic to adult honey bees but highly toxic to larvae.
68

15 SUMMARY

WS uses chemical repellents to manage several bird and mammal species that damage a variety 

of agricultural and non-agricultural resources or pose a risk to human safety (e.g., interfering with 

aircraft). Chemical repellents pose a negligible risk of primary or secondary poisoning to nontarget animals, including scavengers. Label requirements and environmental fate properties

indicate chemical repellents pose no risk to aquatic non-target wildlife. The WS use pattern and

application rates of repellents mostly on private lands result in a negligible risk for the public. The 

dietary risk from chemical repellent exposure to the public is low since most of the repellents are 

considered non-toxic to people, do not threaten drinking water, and many are not used on edible 

plant parts. The risk to WS applicators is also low because they receive training in the product’s 

use and follow label instructions, including appropriate PPE. The release of chemical repellents

into the environment is expected to have no or negligible impacts on non-target species, the 

public, and the environment, including cumulative impacts.

There are uncertainties in this assumption related to differences between taxa. Still, for this risk 

assessment, most chemical repellents are considered practically non-toxic to reptiles and 

terrestrial-phase amphibians when considering the absence of sensitivities to surrogate avian 

species (Table 23). In contrast, several chemical repellents (ammonium soaps of fatty acids, 

anthraquinone, methyl anthranilate, and naphthalene) range from slightly to moderately toxic to 

freshwater fish, indicating similar toxicity to aquatic-phase amphibians. However, thiram is high 

to very highly toxic to fish and aquatic invertebrates (Table 23). 

Although several chemical repellents range in their toxicity to aquatic species (Table 23), aquatic 

exposure from proposed chemical repellent applications is expected to be negligible based on 

the application method, proposed use pattern, label mitigation measures to protect aquatic 

resources, and the chemicals’ environmental fate properties. All repellent applications are made 

by hand or with ground-based equipment.

Most chemical repellents WS proposes to use are practically non-toxic to terrestrial species, 

including mammals and birds (Table 23). Anthraquinone and thiram demonstrate some toxicity to 

terrestrial invertebrates, birds, and mammals. However, the label restrictions, use patterns, and 

environmental fate properties minimize exposure to non-target terrestrial species.
69

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Prevention.

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_____. 2013b. Environmental fate and ecological effects preliminary risk assessment for the registration 

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Acids (EPA-HQ-OPP-2015-0519-0030). U.S. Environmental Protection Agency.

_____. 2015b. Pesticide Retrieval Information System: Hinder, EPA Registration Number 5481-508. U.S. 

Environmental Protection Agency, Office of Chemical Safety and Pollution.

_____. 2015c. Crop Grouping - Part XVD: Apendices for the analysis fo the USDA IR-4 Petition to amend 

the crop group regulation 40 CFR 180.41 (c) (26) and commodity definitions [40 CFR 180.1 (g)] 

related to herb crop group 25 and spice crop group 26. 

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_____. 2015d. Thiram Human Health Assessment Scoping Document in Support of Registration Review 

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_____. 2016a. Problem Formulation for the Ecological RIsk and Drinking Water Exposure Assessments to 

be Conducted for the Registration Review of Naphthalene. 

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_____. 2016b. Predator Urines: Coyote Urines (PC Code: 029007) and Fox Urine (PC Code: 029008) 

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_____. 2019a. Predator Urines: Coyote Urine and Fox Urine Interim Registration Review Decision Case 

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(Americamysis bahia, formerly Mysidopsis bahia). (EPA-HQ-OPP-2015-0433-0032). United States 

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76

17 PREPARERS: WRITERS, EDITORS, AND REVIEWERS

APHIS WS Methods Risk Assessment Committee

Writers for “Use of Chemical Repellents in Wildlife Damage Management Risk 

Assessment”:

Primary Writer: Shelagh DeLiberto 

Position: USDA-APHIS-Wildlife Services (WS), National Wildlife Research Center (NWRC), 

Wildlife Biologist, Fort Collins, CO

Education: BA Biology and Environmental Science – Ithaca College; MS Wildlife Biology –

Colorado State University 

Experience: Sixteen years of service in APHIS conducting wildlife research. Two years of 

experience in preparing categorical exclusions and environmental analyses in compliance 

with the National Environmental Policy Act. 

Primary Writer: Andrea Lemay 

Position: USDA-APHIS-Policy and Program Development (PPD), Environmental and Risk 

Analysis Services (ERAS), Biological Scientist, Raleigh, NC

Education: BS Plant and Soil Science (Biotechnology) - University of Massachusetts; MS Plant 

Pathology -North Carolina State University 

Experience: Thirteen years of service in APHIS conducting risk analysis. Four years of 

experience in preparing environmental analyses in compliance with the National 

Environmental Policy Act.

Writer/Editor: Thomas C. Hall

Position: USDA-APHIS-WS, Operational Support Staff, Staff Wildlife Biologist, Fort Collins, CO

Education: BS Biology (Natural History) and BA Psychology – Fort Lewis College; MS Wildlife 

Ecology – Oklahoma State University

Experience: Special expertise in wildlife biology, identification, ecology, and damage 

management. Thirty-eight years of service in APHIS Wildlife Services including operations 

and research in CO for research and OR, GU, CA, OK, and NV for operations conducting a 

wide variety of programs including bird damage research and management, livestock 

protection (predators and birds), invasive species management, wildlife hazard management 

at airports, property and natural resource protection including waterfowl, brown tree snake, 

feral swine, rodent, and beaver damage management. Researched, applied and supervised 

the use of repellents.

Primary Writer/Editor: Jim Warren 

Position: USDA-APHIS-Policy and Program Development (PPD), Environmental and Risk 

Analysis Services (ERAS), Environmental Toxicologist, Little Rock, AR 

Education: B.S. Forest Ecology and M.S. Entomology – University of Missouri; Ph.D. 

Environmental Toxicology – Clemson University

Experience: Over sixteen years of experience working for APHIS preparing ecological risk 

assessments and providing assistance on environmental compliance. Prior experience before 

joining APHIS includes other government and private sector work regarding ecological risk 

assessments related to various environmental regulations.

Primary Writer: Michael McCaskill
77

Position: USDA-APHIS-Policy and Program Development (PPD), Environmental and Risk 

Analysis Services (ERAS), Toxicologist, New Market, MD

Education: B.S. Environmental Science – University of Florida; MPH Industrial HygieneUniversity of South Carolina, Ph.D. Toxicology-Florida Agriculture and Mechanical University

Experience: Ten years of experience conducting human toxicological research at Florida 

Agriculture and Mechanical University, University of Nebraska Medical Center, and Tulane 

University. Four years of experience conducting human health and environmental 

toxicological risk assessments and assisting environmental compliance programs at the 

Florida Department of Health, Commonwealth of Pennsylvania, and USDA.

Editors/Contributors for “Use of Chemical Repellents in Wildlife Damage Management Risk 

Assessment”:

Primary Writer /Contributor: Emily Ruell 

Position: USDA-APHIS-WS, NWRC, Registration Specialist, Fort Collins, CO

Education: B.S. Zoology and Biological Aspects of Conservation – University of Wisconsin -

Madison; M.S. Ecology – Colorado State University (CSU); M.A. Political Science – CSU

Experience: Nine years of experience with WS NWRC preparing and reviewing vertebrate pesticide 

registration data submissions and other registration materials and providing pesticide regulatory 

guidance to WS, WS NWRC, and collaborators. Prior experience before joining APHIS includes 

seven years of conducting field and laboratory wildlife research at CSU and environmental policy 

research for the U.S. Geological Survey.

Editor: Ryan Wimberly 

Position: USDA-APHIS-WS, Operational Support Staff, Staff Wildlife Biologist, Madison, TN

Education: BS Wildlife Management and Ecology – Northwest Missouri State University

Experience: Special expertise in wildlife biology, ecology, and damage management. Seventeen 

years of service with APHIS Wildlife Services, including operations and research, conducting 

a wide variety of programs, including bird damage research and management, livestock 

protection, invasive species management, wildlife hazard management at airports, property, 

and natural resource protection. Expert in preparing environmental documents for WS 

programs to comply with the National Environmental Policy Act and the Endangered Species 

Act.

Data Contributor: Joey Millison

Position: USDA-APHIS-WS Information and Technology (IT), Junior Applications Developer

Education: Information and Technology coursework from various sources

Experience: Eleven years of experience in APHIS, WS Management Information System (MIS) 

Group. Retrieves WS field data from the MIS for writers, reviewers, and editors.

17.2 Internal Reviewers

USDA APHIS Wildlife Services

Reviewer: Scott Beckerman

Position: USDA APHIS Wildlife Services, State Director/ Supervisory Wildlife Biologist, 

Springfield, IL

Education: BS and MS in Fisheries and Wildlife Management, University of Missouri-Columbia

Experience: Expertise in wildlife damage management and wildlife biology. Thirty one years of 

service in APHIS Wildlife Services operational programs in MO, IA, WI, CA, and IL. 
78

Experience in mitigating conflicts caused by a wide variety of wild animals including, 

ungulates, migratory birds/waterfowl, predators, rodents, and invasive species including feral 

swine.

Reviewer: Scott Werner

Position: USDA-APHIS-WS, National Wildlife Research Center, Supervisory Research Wildlife 

Biologist, Fort Collins, CO.

Education: B.S., M.S., Ph.D. Wildlife and Range Science

Experience: Specialized experience regarding wildlife science and wildlife biology (35 years; 

TWS-Certified Wildlife Biologist®). NWRC research experience, including the evaluation and 

development wildlife repellents for wildlife damage management (25 years).